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Crossover from Universal Depinning to Free Domain-Wall Dynamics in Ultrathin Iron Garnet Films
Authors:
V. Jeudy,
D. Gouéré,
N. Beaulieu,
S. Husain,
R. Dıaz Pardo,
A. Thiaville,
J. Sampaio,
J-M George,
A. Anane,
J. Ben Youssef
Abstract:
Magnetic domain walls display universal, disorder-controlled elastic dynamics at low drive, and texture-governed free motion at high drive. Here, we establish the crossover mechanism between these two regimes. Using experiments in ultrathin epitaxial iron garnet films and Landau-Lifshitz-Gilbert simulations, including disorder, thermal, and internal texture effects, we uncover a disorder- and temp…
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Magnetic domain walls display universal, disorder-controlled elastic dynamics at low drive, and texture-governed free motion at high drive. Here, we establish the crossover mechanism between these two regimes. Using experiments in ultrathin epitaxial iron garnet films and Landau-Lifshitz-Gilbert simulations, including disorder, thermal, and internal texture effects, we uncover a disorder- and temperature-dependent precessional flow that bridges pinned and free dynamics. We further demonstrate that the exceptionally low pinning in garnets arises from the weak coupling between domain walls and disorder, together with a correlation length that exceeds the wall width.
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Submitted 4 December, 2025;
originally announced December 2025.
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Effects of antiferromagnetic coupling and pinning on domain wall dynamics in synthetic ferrimagnets
Authors:
Sougata Mallick,
Nicolas Reyren,
André Thiaville,
Philippe Ohresser,
Nicolas Jaouen,
Vincent Cros,
Vincent Jeudy
Abstract:
Domain wall (DW) dynamics in antiferromagnetic (AFM) systems offer the advantages over their ferromagnetic counterparts of having faster and more energy efficient manipulation due to the absence of net magnetization, leading to reduced magnetic crosstalk and improved performance in spintronic devices. A comprehensive analysis of DW dynamics across regimes such as creep, depinning, and flow is well…
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Domain wall (DW) dynamics in antiferromagnetic (AFM) systems offer the advantages over their ferromagnetic counterparts of having faster and more energy efficient manipulation due to the absence of net magnetization, leading to reduced magnetic crosstalk and improved performance in spintronic devices. A comprehensive analysis of DW dynamics across regimes such as creep, depinning, and flow is well established in ferromagnetic systems but remains lacking in AFM-coupled systems. In this study, we explore the nature of DW dynamics in synthetic ferrimagnetic multilayers composed of Pt|Co|Tb|Al for different Tb thickness, focusing on the underlying pinning parameters, and on the different regimes of DW dynamics driven by spin-orbit torques (SOTs). We find that due to the AFM coupling between Co and Tb, the magnetic moment of Tb increases with Tb thickness resulting in a reduced saturation magnetization and an enhanced depinning field. The DW disorder interaction is found to vary weakly with the AFM coupling between Co and Tb, while the complete withdrawal of the Tb layer strongly increases the anisotropy and the DW pinning. Furthermore, we propose a novel approach to measure effective SOTs by comparing depinning transitions in current and field-induced DW motion. This research reveals new insights into DW dynamics in coupled AFM systems, highlighting enhancements in mobility through optimized SOTs and pinning landscapes.
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Submitted 17 February, 2025;
originally announced February 2025.
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Domain-wall Magnetic-texture dependent Creep Motion driven by Spin-transfer Torques
Authors:
Lucas Javier Albornoz,
Rebeca Díaz Pardo,
Aristide Lemaître,
Sebastian Bustingorry,
Javier Curiale,
Vincent Jeudy
Abstract:
We explore the contributions of adiabatic and non-adiabatic spin-transfer torques (STT) of a spin-polarized current to the thermally activated creep motion of domain-walls in a thin (Ga,Mn)(As,P) film with perpendicular anisotropy. For a domain-wall transverse to current, the non-adiabatic STT is found to act as an external magnetic field. Close to the compensation between these two terms, the adi…
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We explore the contributions of adiabatic and non-adiabatic spin-transfer torques (STT) of a spin-polarized current to the thermally activated creep motion of domain-walls in a thin (Ga,Mn)(As,P) film with perpendicular anisotropy. For a domain-wall transverse to current, the non-adiabatic STT is found to act as an external magnetic field. Close to the compensation between these two terms, the adiabatic contribution is strongly enhanced. The domain-wall velocity may be both increased or reduced by the adiabatic STT, which we associate to variations of creep pinning energy barrier with domain-wall magnetic texture. Far from compensation, the contribution of adiabatic STT is negligible. Field and current driven domain-wall motion present common universal behaviors described by the quenched Edwards Wilkinson universality class.
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Submitted 24 December, 2023;
originally announced December 2023.
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Driving skyrmions in flow regime in synthetic ferrimagnets
Authors:
Sougata Mallick,
Yanis Sassi,
Nicholas Figueiredo Prestes,
Sachin Krishnia,
Fernando Gallego,
Thibaud Denneulin,
Sophie Collin,
Karim Bouzehouane,
André Thiaville,
Rafal E. Dunin-Borkowski,
Vincent Jeudy,
Albert Fert,
Nicolas Reyren,
Vincent Cros
Abstract:
Despite significant advances in the last decade regarding the room temperature stabilization of skyrmions or their current induced dynamics, the impact of local material inhomogeneities still remains an important issue that impedes to reach the regime of steady state motion of these spin textures. Here, we study the spin-torque driven motion of skyrmions in synthetic ferrimagnetic multilayers with…
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Despite significant advances in the last decade regarding the room temperature stabilization of skyrmions or their current induced dynamics, the impact of local material inhomogeneities still remains an important issue that impedes to reach the regime of steady state motion of these spin textures. Here, we study the spin-torque driven motion of skyrmions in synthetic ferrimagnetic multilayers with the aim of achieving high mobility and reduced skyrmion Hall effect. We consider Pt|Co|Tb multilayers of various thicknesses with antiferromagnetic coupling between the Co and Tb magnetization. The increase of Tb thickness in the multilayers allows to reduce the total magnetic moment and increases the spin-orbit torques allowing to reach velocities up to 400 m.s-1 for skyrmions with diameters of about 160 nm. We demonstrate that due to reduced skyrmion Hall effect, combined with the edge repulsion of the magnetic track making the skyrmions moving along the track without any transverse deflection. Further, by comparing the field-induced domain wall motion and current-induced skyrmion motion, we demonstrate that the skyrmions at the largest current densities present all the characteristics of a dynamical flow regime.
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Submitted 1 June, 2023; v1 submitted 30 May, 2023;
originally announced May 2023.
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Control of domain wall and pinning disorder interaction by light He$^+$ ion irradiation in Pt/Co/AlOx ultrathin films
Authors:
Cristina Balan,
Johannes W. van der Jagt,
Jose Peña Garcia,
Jan Vogel,
Laurent Ranno,
Marlio Bonfim,
Dafiné Ravelosona,
Stefania Pizzini,
Vincent Jeudy
Abstract:
We have studied the effect of He$^+$ irradiation on the dynamics of chiral domain walls in Pt/Co/AlOx trilayers in the creep regime. The irradiation leads to a strong decrease of the depinning field and a non-monotonous change of the effective pinning barriers. The variations of domain wall dynamics result essentially from the strong decrease of the effective anisotropy constant, which increases t…
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We have studied the effect of He$^+$ irradiation on the dynamics of chiral domain walls in Pt/Co/AlOx trilayers in the creep regime. The irradiation leads to a strong decrease of the depinning field and a non-monotonous change of the effective pinning barriers. The variations of domain wall dynamics result essentially from the strong decrease of the effective anisotropy constant, which increases the domain wall width. The latter is found to present a perfect scaling with the length-scale of the interaction between domain wall and disorder, $ξ$. On the other hand, the strength of the domain wall-disorder interaction, $f_{pin}$, is weakly impacted by the irradiation, suggesting that the length-scales of the disorder fluctuation remain smaller than the domain wall width.
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Submitted 8 March, 2023;
originally announced March 2023.
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Improving Néel domain walls dynamics and skyrmion stability using He ion irradiation
Authors:
Cristina Balan,
Johannes W. van der Jagt,
Aymen Fassatoui,
Jose Peña Garcia,
Vincent Jeudy,
André Thiaville,
Jan Vogel,
Marlio Bonfim,
Laurent Ranno,
Dafiné Ravelosona,
Stefania Pizzini
Abstract:
Magnetization reversal and domain wall dynamics in Pt/Co/AlOx trilayers have been tuned by He+ ion irradiation. Fluences up to 1.5x10$^{15}$ ions/cm$^2$ strongly decrease the perpendicular magnetic anisotropy (PMA), without affecting neither the spontaneous magnetization nor the strength of the Dzyaloshinskii-Moriya interaction (DMI). This confirms the robustness of the DMI interaction against int…
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Magnetization reversal and domain wall dynamics in Pt/Co/AlOx trilayers have been tuned by He+ ion irradiation. Fluences up to 1.5x10$^{15}$ ions/cm$^2$ strongly decrease the perpendicular magnetic anisotropy (PMA), without affecting neither the spontaneous magnetization nor the strength of the Dzyaloshinskii-Moriya interaction (DMI). This confirms the robustness of the DMI interaction against interfacial chemical intermixing, already predicted by theory. In parallel with the decrease of the PMA in the irradiated samples, a strong decrease of the depinning field is observed. This allows the domain walls to reach large maximum velocities with lower magnetic fields with respect to those needed for the pristine films. Decoupling PMA from DMI can therefore be beneficial for the design of low energy devices based on domain wall dynamics. When the samples are irradiated with larger He+ fluences, the magnetization gets close to the out-of-plane/in-plane reorientation transition where 100nm size magnetic skyrmions are stabilized. We observe that as the He+ fluence increases, the skyrmion size decreases while these magnetic textures become more stable against the application of an external magnetic field.
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Submitted 8 March, 2023;
originally announced March 2023.
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Revealing nanoscale disorder in W/CoFeB/MgO ultra-thin films using domain wall motion
Authors:
Johannes Wilhelmus van der Jagt,
Vincent Jeudy,
André Thiaville,
Mamour Sall,
Nicolas Vernier,
Liza Herrera Diez,
Mohamed Belmeguenai,
Yves Roussigné,
Salim M. Chérif,
Mouad Fattouhi,
Luis Lopez-Diaz,
Alessio Lamperti,
Roméo Juge,
Dafiné Ravelosona
Abstract:
Disorder in ultra-thin magnetic films can significantly hinder domain wall motion. One of the main issues on the path towards efficient domain wall based devices remains the characterization of the pinning landscape at the nanoscale. In this paper, we study domain wall motion in W/CoFeB/MgO thin films with perpendicular magnetic anisotropy crystallized by annealing at 400$^{\circ}$C and a process…
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Disorder in ultra-thin magnetic films can significantly hinder domain wall motion. One of the main issues on the path towards efficient domain wall based devices remains the characterization of the pinning landscape at the nanoscale. In this paper, we study domain wall motion in W/CoFeB/MgO thin films with perpendicular magnetic anisotropy crystallized by annealing at 400$^{\circ}$C and a process based on He$^{+}$ irradiation combined with elevated temperatures. Magnetic properties are similar for the whole series of samples, while the magnetic domain wall mobility is critically improved in the irradiated samples. By using an analytical model to extract nanoscale pinning parameters, we reveal important variations in the disorder of the crystallized samples. This work offers a unique opportunity to selectively analyze the effects of disorder on the domain wall dynamics, without the contribution of changes in the magnetic properties. Our results highlight the importance of evaluating the nanoscale pinning parameters of the material when designing devices based on domain wall motion, which in return can be a powerful tool to probe the disorder in ultra-thin magnetic films.
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Submitted 19 August, 2022;
originally announced August 2022.
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Domain-wall roughness in GdFeCo thin films: crossover length scales and roughness exponents
Authors:
Lucas J. Albornoz,
Pamela C. Guruciaga,
Vincent Jeudy,
Javier Curiale,
Sebastian Bustingorry
Abstract:
Domain-wall dynamics and spatial fluctuations are closely related to each other and to universal features of disordered systems. Experimentally measured roughness exponents characterizing spatial fluctuations have been reported for magnetic thin films, with values generally different from those predicted by the equilibrium, depinning and thermal reference states. Here, we study the roughness of do…
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Domain-wall dynamics and spatial fluctuations are closely related to each other and to universal features of disordered systems. Experimentally measured roughness exponents characterizing spatial fluctuations have been reported for magnetic thin films, with values generally different from those predicted by the equilibrium, depinning and thermal reference states. Here, we study the roughness of domain walls in GdFeCo thin films over a large range of magnetic field and temperature. Our analysis is performed in the framework of a model considering length-scale crossovers between the reference states, which is shown to bridge the differences between experimental results and theoretical predictions. We also quantify for the first time the size of the depinning avalanches below the depinning field at finite temperatures.
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Submitted 8 July, 2021; v1 submitted 12 April, 2021;
originally announced April 2021.
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Chiral magnetic domain walls under transverse fields: a semi-analytical model
Authors:
Pierre Géhanne,
André Thiaville,
Stanislas Rohart,
Vincent Jeudy
Abstract:
An analytical model for the domain wall structure in ultrathin films with perpendicular easy axis and interfacial Dzyaloshinskii-Moriya interaction, submitted to an arbitrary in-plane magnetic field, is presented. Its solution is simplified to the numerical minimization of an analytic function of just one variable. The model predictions are compared to numerical micromagnetic simulations, using pa…
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An analytical model for the domain wall structure in ultrathin films with perpendicular easy axis and interfacial Dzyaloshinskii-Moriya interaction, submitted to an arbitrary in-plane magnetic field, is presented. Its solution is simplified to the numerical minimization of an analytic function of just one variable. The model predictions are compared to numerical micromagnetic simulations, using parameters of existing samples, revealing a very good agreement. Remaining differences are analyzed, and partly corrected. Differences with the predictions of the simplest model, usually found in the literature, in which only the domain wall moment's in-plane orientation can vary, are exemplified. The model allows accurate computations, as a function of in-plane field module and orientation, of the domain wall tension and width, quantities controlling the creep motion of domain walls in such films.
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Submitted 25 March, 2021;
originally announced March 2021.
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Universal Critical Exponents of the Magnetic Domain Wall Depinning Transition
Authors:
Lucas J. Albornoz,
Ezequiel E. Ferrero,
Alejandro B. Kolton,
Vincent Jeudy,
Sebastian Bustingorry,
Javier Curiale
Abstract:
Magnetic field driven domain wall dynamics in a ferrimagnetic GdFeCo thin film with perpendicular magnetic anisotropy is studied using low temperature magneto-optical Kerr microscopy. Measurements performed in a practically athermal condition allow for the direct experimental determination of the velocity ($ β= 0.30 \pm 0.03 $) and correlation length ($ ν= 1.3 \pm 0.3 $) exponents of the depinning…
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Magnetic field driven domain wall dynamics in a ferrimagnetic GdFeCo thin film with perpendicular magnetic anisotropy is studied using low temperature magneto-optical Kerr microscopy. Measurements performed in a practically athermal condition allow for the direct experimental determination of the velocity ($ β= 0.30 \pm 0.03 $) and correlation length ($ ν= 1.3 \pm 0.3 $) exponents of the depinning transition. The whole family of exponents characterizing the transition is deduced, providing evidence that the depinning of magnetic domain walls is better described by the quenched Edwards-Wilkinson universality class.
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Submitted 15 July, 2021; v1 submitted 16 January, 2021;
originally announced January 2021.
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Strength and length-scale of the interaction between domain walls and pinning disorder in thin ferromagnetic films
Authors:
P. Géhanne,
S. Rohart,
A. Thiaville,
V. Jeudy
Abstract:
We explore the magnetic-field-driven motion of domain walls with different chiralities in thin ferromagnetic films made of Pt/Co/Pt, Au/Co/Pt, and Pt/Co/Au. From the analysis of domain wall dynamics, we extract parameters characterizing the interaction between domain walls and weak pinning disorder of the films. The variations of domain wall structure, controlled by an in-plane field, are found to…
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We explore the magnetic-field-driven motion of domain walls with different chiralities in thin ferromagnetic films made of Pt/Co/Pt, Au/Co/Pt, and Pt/Co/Au. From the analysis of domain wall dynamics, we extract parameters characterizing the interaction between domain walls and weak pinning disorder of the films. The variations of domain wall structure, controlled by an in-plane field, are found to modify the characteristic length-scale of pinning in strong correlation with the domain wall width, whatever its chirality and the interaction strength between domain walls and pinning defects. These findings should be also relevant for a wide variety of elastic interfaces moving in weak pinning disordered media.
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Submitted 28 September, 2020; v1 submitted 18 May, 2020;
originally announced May 2020.
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Tuning Ginzburg-Landau theory to quantitatively study thin ferromagnetic materials
Authors:
Pamela C. Guruciaga,
Nirvana Caballero,
Vincent Jeudy,
Javier Curiale,
Sebastian Bustingorry
Abstract:
Along with experiments, numerical simulations are key to gaining insight into the underlying mechanisms governing domain wall motion in thin ferromagnetic systems. However, a direct comparison between numerical simulation of model systems and experimental results still represents a great challenge. Here, we present a tuned Ginzburg-Landau model to quantitatively study the dynamics of domain walls…
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Along with experiments, numerical simulations are key to gaining insight into the underlying mechanisms governing domain wall motion in thin ferromagnetic systems. However, a direct comparison between numerical simulation of model systems and experimental results still represents a great challenge. Here, we present a tuned Ginzburg-Landau model to quantitatively study the dynamics of domain walls in quasi two-dimensional ferromagnetic systems with perpendicular magnetic anisotropy. This model incorporates material and experimental parameters and the micromagnetic prescription for thermal fluctuations, allowing us to perform material-specific simulations and at the same time recover universal features. We show that our model quantitatively reproduces previous experimental velocity-field data in the archetypal perpendicular magnetic anisotropy Pt/Co/Pt ultra-thin films in the three dynamical regimes of domain wall motion (creep, depinning and flow). In addition, we present a statistical analysis of the domain wall width parameter, showing that our model can provide detailed nano-scale information while retaining the complex behavior of a statistical disordered model.
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Submitted 18 November, 2020; v1 submitted 19 December, 2019;
originally announced December 2019.
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Common universal behaviors of magnetic domain walls driven by spin-polarized electrical current and magnetic field
Authors:
R. Diaz Pardo,
N. Moisan,
L. Albornoz,
A. Lemaitre,
J. Curiale,
V. Jeudy
Abstract:
We explore universal behaviors of magnetic domain wall driven by the spin-transfer of an electrical current, in a ferromagnetic (Ga,Mn)(As,P) thin film with perpendicular magnetic anisotropy. For a current direction transverse to domain wall, the dynamics of the thermally activated creep regime and the depinning transition are found to be compatible with a self-consistent universal description of…
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We explore universal behaviors of magnetic domain wall driven by the spin-transfer of an electrical current, in a ferromagnetic (Ga,Mn)(As,P) thin film with perpendicular magnetic anisotropy. For a current direction transverse to domain wall, the dynamics of the thermally activated creep regime and the depinning transition are found to be compatible with a self-consistent universal description of magnetic field induced domain wall dynamics. This common universal behavior, characteristic of the so-called quenched Edwards-Wilkinson universality class, is confirmed by a complementary and independent analysis of domain wall roughness. However, the tilting of domain walls and the formation of facets is produced by the directionality of interaction with the current, which acts as a magnetic field only in the direction transverse to domain wall.
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Submitted 5 September, 2019; v1 submitted 5 April, 2019;
originally announced April 2019.
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Universal dimensional crossover of domain wall dynamics in ferromagnetic films
Authors:
W. Savero Torres,
R. Diaz Pardo,
S. Bustingorry,
A. B. Kolton,
A. Lemaître,
V. Jeudy
Abstract:
The magnetic domain wall motion driven by a magnetic field is studied in (Ga,Mn)As and (Ga,Mn)(As,P) films of different thicknesses. In the thermally activated creep regime, a kink in the velocity curves and a jump of the roughness exponent evidence a dimensional crossover in the domain wall dynamics. The measured values of the roughness exponent zeta_{1d} = 0.62 +/- 0.02 and zeta_{2d} = 0.45 +/-…
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The magnetic domain wall motion driven by a magnetic field is studied in (Ga,Mn)As and (Ga,Mn)(As,P) films of different thicknesses. In the thermally activated creep regime, a kink in the velocity curves and a jump of the roughness exponent evidence a dimensional crossover in the domain wall dynamics. The measured values of the roughness exponent zeta_{1d} = 0.62 +/- 0.02 and zeta_{2d} = 0.45 +/- 0.04 are compatible with theoretical predictions for the motion of elastic line (d = 1) and surface (d = 2) in two and three dimensional media, respectively.
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Submitted 1 December, 2018; v1 submitted 26 November, 2018;
originally announced November 2018.
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Domain Wall Motion and Interfacial Dzyaloshinskii-Moriya Interactions in Pt/Co/Ir$(t_\mathrm{Ir})$/Ta Multilayers
Authors:
Kowsar Shahbazi,
Joo-Von Kim,
Hans T. Nembach,
Justin M. Shaw,
Andreas Bischof,
Marta D. Rossell,
Vincent Jeudy,
Thomas A. Moore,
Christopher H. Marrows
Abstract:
The interfacial Dzyaloshinskii-Moriya interaction (DMI) is important for chiral domain walls (DWs) and for stabilizing magnetic skyrmions. We study the effects of introducing increasing thicknesses of Ir, from zero to 2 nm, into a Pt/Co/Ta multilayer between the Co and Ta. We observe a marked increase in magnetic moment, due to the suppression of the dead layer at the interface with Ta, but the pe…
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The interfacial Dzyaloshinskii-Moriya interaction (DMI) is important for chiral domain walls (DWs) and for stabilizing magnetic skyrmions. We study the effects of introducing increasing thicknesses of Ir, from zero to 2 nm, into a Pt/Co/Ta multilayer between the Co and Ta. We observe a marked increase in magnetic moment, due to the suppression of the dead layer at the interface with Ta, but the perpendicular anisotropy is hardly affected. All samples show a universal scaling of the field-driven domain wall velocity across the creep and depinning regimes. Asymmetric bubble expansion shows that DWs in all of the samples have the left-handed Néel form. The value of in-plane field at which the creep velocity shows a minimum drops markedly on the introduction of Ir, as does the frequency shift of the Stokes and anti-Stokes peaks in Brillouin light scattering measurements. Despite this qualitative similarity, there are quantitative differences in the DMI strength given by the two measurements, with BLS often returning higher values. Many features in bubble expansion velocity curves do not fit simple models commonly used to date, namely a lack of symmetry about the velocity minimum and no difference in velocities at high in-plane field. These features are explained by the use of a model in which the depinning field is allowed to vary with in-plane field in a way determined from micromagnetic simulations. This theory shows that velocity minimum underestimates the DMI field, consistent with BLS returning higher values. Our results suggest that the DMI at an Ir/Co interface has the same sign as the DMI at a Pt/Co interface.
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Submitted 8 October, 2018;
originally announced October 2018.
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Magnetic properties and field-driven dynamics of chiral domain walls in epitaxial Pt/Co/Au$_x$Pt$_{1-x}$ trilayers
Authors:
Kowsar Shahbazi,
Aleš Hrabec,
Simone Moretti,
Michael B. Ward,
Thomas A. Moore,
Vincent Jeudy,
Eduardo Martinez,
Christopher H. Marrows
Abstract:
Chiral domain walls in ultrathin perpendicularly magnetised layers have a Néel structure stabilised by a Dzyaloshinskii-Moriya interaction (DMI) that is generated at the interface between the ferromagnet and a heavy metal. Different heavy metals are required above and below a ferromagnetic film in order to generate the structural inversion asymmetry needed to ensure that the DMI arising at the two…
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Chiral domain walls in ultrathin perpendicularly magnetised layers have a Néel structure stabilised by a Dzyaloshinskii-Moriya interaction (DMI) that is generated at the interface between the ferromagnet and a heavy metal. Different heavy metals are required above and below a ferromagnetic film in order to generate the structural inversion asymmetry needed to ensure that the DMI arising at the two interfaces does not cancel. Here we report on the magnetic properties of epitaxial Pt/Co/Au$_x$Pt$_{1-x}$ trilayers grown by sputtering onto sapphire substrates with 0.6 nm thick Co. As $x$ rises from 0 to 1 a structural inversion asymmetry is generated. We characterise the epilayer structure with x-ray diffraction and cross-sectional transmission electron microscopy, revealing (111) stacking. The saturation magnetization falls as the proximity magnetisation in Pt is reduced, whilst the perpendicular magnetic anisotropy $K_\mathrm{u}$ rises. The micromagnetic DMI strength $D$ was determined using the bubble expansion technique and also rises from a negligible value when $x=0$ to $\sim 1$ mJ/m$^2$ for $x = 1$. The depinning field at which field-driven domain wall motion crosses from the creep to the depinning regime rises from $\sim 40$ to $\sim 70$ mT, attributed to greater spatial fluctuations of the domain wall energy with increasing Au concentration. Meanwhile, the increase in DMI causes the Walker field to rise from $\sim 10$ to $\sim 280$ mT, meaning that only in the $x = 1$ sample is the steady flow regime accessible. The full dependence of domain wall velocity on driving field bears little resemblance to the prediction of a simple one-dimensional model, but can be described very well using micromagnetic simulations with a realistic model of disorder. These reveal a rise in Gilbert damping as $x$ increases.
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Submitted 8 November, 2018; v1 submitted 10 September, 2018;
originally announced September 2018.
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Intermittent collective dynamics of domain walls in the creep regime
Authors:
Matías Pablo Grassi,
Alejandro B. Kolton,
Vincent Jeudy,
Alexandra Mougin,
Sebastian Bustingorry,
Javier Curiale
Abstract:
We study the ultra slow domain wall motion in ferromagnetic thin films driven by a weak magnetic field. Using time resolved magneto-optical Kerr effect microscopy, we access to the statistics of the intermittent thermally activated domain wall jumps between deep metastable states. Our observations are consistent with the existence of creep avalanches: roughly independent clusters with broad size a…
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We study the ultra slow domain wall motion in ferromagnetic thin films driven by a weak magnetic field. Using time resolved magneto-optical Kerr effect microscopy, we access to the statistics of the intermittent thermally activated domain wall jumps between deep metastable states. Our observations are consistent with the existence of creep avalanches: roughly independent clusters with broad size and ignition waiting-time distributions, each one composed by a large number of spatio-temporally correlated thermally activated elementary events. Moreover, we evidence that the large scale geometry of domain walls is better described by depinning rather than equilibrium universal exponents.
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Submitted 7 December, 2018; v1 submitted 25 April, 2018;
originally announced April 2018.
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Magnetic domain wall creep and depinning: a scalar field model approach
Authors:
Nirvana B. Caballero,
Ezequiel E. Ferrero,
Alejandro B. Kolton,
Javier Curiale,
Vincent Jeudy,
Sebastian Bustingorry
Abstract:
Magnetic domain wall motion is at the heart of new magneto-electronic technologies and hence the need for a deeper understanding of domain wall dynamics in magnetic systems. In this context, numerical simulations using simple models can capture the main ingredients responsible for the complex observed domain wall behavior. We present a scalar-field model for the magnetization dynamics of quasi-two…
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Magnetic domain wall motion is at the heart of new magneto-electronic technologies and hence the need for a deeper understanding of domain wall dynamics in magnetic systems. In this context, numerical simulations using simple models can capture the main ingredients responsible for the complex observed domain wall behavior. We present a scalar-field model for the magnetization dynamics of quasi-two-dimensional systems with a perpendicular easy axis of magnetization which allows a direct comparison with typical experimental protocols, used in polar magneto-optical Kerr effect microscopy experiments. We show that the thermally activated creep and depinning regimes of domain wall motion can be reached, and the effect of different quenched disorder implementations can be assessed with the model. In particular, we show that the depinning field increases with the mean grain size of a Voronoi tessellation model for the disorder.
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Submitted 22 January, 2018;
originally announced January 2018.
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Pinning of Domain Walls in thin Ferromagnetic Films
Authors:
Vincent Jeudy,
Rebeca Diaz Pardo,
Williams Savero Torres,
Sebastian Bustingorry,
Alejandro Kolton
Abstract:
We present a quantitative investigation of magnetic domain wall pinning in thin magnets with perpendicular anisotropy. A self-consistent description exploiting the universal features of the depinning and thermally activated sub-threshold creep regimes observed in the field driven domain wall velocity, is used to determine the effective pinning parameters controlling the domain wall dynamics: the e…
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We present a quantitative investigation of magnetic domain wall pinning in thin magnets with perpendicular anisotropy. A self-consistent description exploiting the universal features of the depinning and thermally activated sub-threshold creep regimes observed in the field driven domain wall velocity, is used to determine the effective pinning parameters controlling the domain wall dynamics: the effective height of pinning barriers, the depinning threshold, and the velocity at depinning. Within this framework, the analysis of results published in the literature allows for a quantitative comparison of pinning properties for a set of magnetic materials in a wide temperature range. On the basis of scaling arguments, the microscopic parameters controlling the pinning: the correlation length of pinning, the collectively pinned domain wall length (Larkin length) and the strength of pinning disorder, are estimated from the effective pinning and the micromagnetic parameters. The analysis of thermal effects reveals a crossover between different pinning length scales and strengths at low reduced temperature.
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Submitted 17 May, 2018; v1 submitted 23 September, 2017;
originally announced September 2017.
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Excess velocity of magnetic domain walls close to the depinning field
Authors:
Nirvana B. Caballero,
Iván Fernández Aguirre,
Lucas J. Albornoz,
Alejandro B. Kolton,
Juan Carlos Rojas-Sánchez,
Sophie Collin,
Jean Marie George,
Rebeca Diaz Pardo,
Vincent Jeudy,
Sebastian Bustingorry,
Javier Curiale
Abstract:
Magnetic field driven domain wall velocities in [Co/Ni] based multilayers thin films have been measured using polar magneto-optic Kerr effect microscopy. The low field results are shown to be consistent with the universal creep regime of domain wall motion, characterized by a stretched exponential growth of the velocity with the inverse of the applied field. Approaching the depinning field from be…
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Magnetic field driven domain wall velocities in [Co/Ni] based multilayers thin films have been measured using polar magneto-optic Kerr effect microscopy. The low field results are shown to be consistent with the universal creep regime of domain wall motion, characterized by a stretched exponential growth of the velocity with the inverse of the applied field. Approaching the depinning field from below results in an unexpected excess velocity with respect to the creep law. We analyze these results using scaling theory to show that this speeding up of domain wall motion can be interpreted as due to the increase of the size of the deterministic relaxation close to the depinning transition. We propose a phenomenological model which allows to accurately fit the observed excess velocity and to obtain characteristic values for the depinning field $H_d$, the depinning temperature $T_d$, and the characteristic velocity scale $v_0$ for each sample.
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Submitted 23 January, 2018; v1 submitted 11 August, 2017;
originally announced August 2017.
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Universal Depinning Transition of Domain Walls in Ultrathin Ferromagnets
Authors:
Rebeca Diaz Pardo,
Williams Savero Torres,
Alejandro Kolton,
Sebastian Bustingorry,
Vincent Jeudy
Abstract:
We present a quantitative and comparative study of magnetic field driven domain wall depinning transition in different ferromagnetic ultrathin films over a wide range of temperature. We reveal a universal scaling function accounting for both drive and thermal effects on the depinning transition, including critical exponents. The consistent description we obtain for both the depinning and subthresh…
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We present a quantitative and comparative study of magnetic field driven domain wall depinning transition in different ferromagnetic ultrathin films over a wide range of temperature. We reveal a universal scaling function accounting for both drive and thermal effects on the depinning transition, including critical exponents. The consistent description we obtain for both the depinning and subthreshold thermally activated creep motion should shed light on the universal glassy dynamics of thermally fluctuating elastic objects pinned by disordered energy landscapes.
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Submitted 3 February, 2017; v1 submitted 26 November, 2016;
originally announced November 2016.
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Universal pinning energy barrier for driven domain walls in thin ferromagnetic films
Authors:
Vincent Jeudy,
Alexandra Mougin,
Sebastian Bustingorry,
Williams Savero Torres,
Jon Gorchon,
Alejandro Kolton,
Aristide Lemaître,
Jean-Pierre Jamet
Abstract:
We report a comparative study of magnetic field driven domain wall motion in thin films made of different magnetic materials for a wide range of field and temperature. The full thermally activated creep motion, observed below the depinning threshold, is shown to be described by a unique universal energy barrier function. Our findings should be relevant for other systems whose dynamics can be model…
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We report a comparative study of magnetic field driven domain wall motion in thin films made of different magnetic materials for a wide range of field and temperature. The full thermally activated creep motion, observed below the depinning threshold, is shown to be described by a unique universal energy barrier function. Our findings should be relevant for other systems whose dynamics can be modeled by elastic interfaces moving on disordered energy landscapes.
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Submitted 4 March, 2016;
originally announced March 2016.
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Current Induced Fingering Instability in Magnetic Domain Walls
Authors:
Jon Gorchon,
Javier Curiale,
Andrejs Cebers,
Aristide Lemaître,
Nicolas Vernier,
Mathis Plapp,
Vincent Jeudy
Abstract:
The shape instability of magnetic domain walls under current is investigated in a ferromagnetic (Ga,Mn)(As,P) film with perpendicular anisotropy. Domain wall motion is driven by the spin transfer torque mechanism. A current density gradient is found either to stabilize domains with walls perpendicular to current lines or to produce finger-like patterns, depending on the domain wall motion directio…
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The shape instability of magnetic domain walls under current is investigated in a ferromagnetic (Ga,Mn)(As,P) film with perpendicular anisotropy. Domain wall motion is driven by the spin transfer torque mechanism. A current density gradient is found either to stabilize domains with walls perpendicular to current lines or to produce finger-like patterns, depending on the domain wall motion direction. The instability mechanism is shown to result from the non-adiabatic contribution of the spin transfer torque mechanism.
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Submitted 17 June, 2015; v1 submitted 3 September, 2014;
originally announced September 2014.
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Pinning dependent field driven domain wall dynamics and thermal scaling in an ultrathin Pt/Co/Pt magnetic film
Authors:
J. Gorchon,
S. Bustingorry,
J. Ferré,
V. Jeudy,
A. B. Kolton,
T. Giamarchi
Abstract:
Magnetic field-driven domain wall motion in an ultrathin Pt/Co(0.45nm)/Pt ferromagnetic film with perpendicular anisotropy is studied over a wide temperature range. Three different pinning dependent dynamical regimes are clearly identified: the creep, the thermally assisted flux flow and the depinning, as well as their corresponding crossovers. The wall elastic energy and microscopic parameters ch…
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Magnetic field-driven domain wall motion in an ultrathin Pt/Co(0.45nm)/Pt ferromagnetic film with perpendicular anisotropy is studied over a wide temperature range. Three different pinning dependent dynamical regimes are clearly identified: the creep, the thermally assisted flux flow and the depinning, as well as their corresponding crossovers. The wall elastic energy and microscopic parameters characterizing the pinning are determined. Both the extracted thermal rounding exponent at the depinning transition, $ψ=$0.15, and the Larkin length crossover exponent, $φ=$0.24, fit well with the numerical predictions.
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Submitted 29 July, 2014;
originally announced July 2014.
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Modified current induced domain wall motion in GaMnAs nanowire
Authors:
Nicolas Vernier,
Jean-Paul Adam,
Andre Thiaville,
Vincent Jeudy,
Aristide Lemaitre,
Jacques Ferré,
Giancarlo Faini
Abstract:
We report on current induced domain wall propagation in a patterned GaMnAs microwire with perpendicular magnetization. An unexpected slowing down of the propagation velocity has been found when the moving domain wall extends over only half of the width of the wire. This slowing down is related to the elongation of a longitudinal wall along the axis of the wire. By using an energy balance argument,…
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We report on current induced domain wall propagation in a patterned GaMnAs microwire with perpendicular magnetization. An unexpected slowing down of the propagation velocity has been found when the moving domain wall extends over only half of the width of the wire. This slowing down is related to the elongation of a longitudinal wall along the axis of the wire. By using an energy balance argument, the expected theoretical dependence of the velocity change has been calculated and compared with the experimental results. According to this, the energy associated to the longitudinal domain wall should change when a current passes through the wire. These results provide possible evidence of transverse spin diffusion along a longitudinal domain wall.
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Submitted 25 March, 2013;
originally announced March 2013.
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Electric-field control of the magnetic anisotropy in an ultrathin (Ga,Mn)As/(Ga,Mn)(As,P) bilayer
Authors:
Tarik Niazi,
Mathieu Cormier,
Damien Lucot,
Ludovic Largeau,
Vincent Jeudy,
Joel Cibert,
Aristide Lemaître
Abstract:
We report on the electric control of the magnetic anisotropy in an ultrathin ferromagnetic (Ga,Mn)As/(Ga,Mn)(As,P) bilayer with competing in-plane and out-of-plane anisotropies. The carrier distribution and therefore the strength of the effective anisotropy is controlled by the gate voltage of a field effect device. Anomalous Hall Effect measurements confirm that a depletion of carriers in the upp…
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We report on the electric control of the magnetic anisotropy in an ultrathin ferromagnetic (Ga,Mn)As/(Ga,Mn)(As,P) bilayer with competing in-plane and out-of-plane anisotropies. The carrier distribution and therefore the strength of the effective anisotropy is controlled by the gate voltage of a field effect device. Anomalous Hall Effect measurements confirm that a depletion of carriers in the upper (Ga,Mn)As layer results in the decrease of the in-plane anisotropy. The uniaxial anisotropy field is found to decrease by a factor ~ 4 over the explored gate-voltage range, so that the transition to an out-of-plane easy-axis configuration is almost reached.
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Submitted 29 November, 2012;
originally announced November 2012.
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Field-Driven Domain-Wall Dynamics in GaMnAs Films with Perpendicular Anisotropy
Authors:
Alexandre Dourlat,
Vincent Jeudy,
Aristide Lemaître,
Catherine Gourdon
Abstract:
We combine magneto-optical imaging and a magnetic field pulse technique to study domain wall dynamics in a ferromagnetic (Ga,Mn)As layer with perpendicular easy axis. Contrary to ultrathin metallic layers, the depinning field is found to be smaller than the Walker field, thereby allowing for the observation of the steady and precessional flow regimes. The domain wall width and damping parameters…
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We combine magneto-optical imaging and a magnetic field pulse technique to study domain wall dynamics in a ferromagnetic (Ga,Mn)As layer with perpendicular easy axis. Contrary to ultrathin metallic layers, the depinning field is found to be smaller than the Walker field, thereby allowing for the observation of the steady and precessional flow regimes. The domain wall width and damping parameters are determined self-consistently. The damping, 30 times larger than the one deduced from ferromagnetic resonance, is shown to essentially originate from the non-conservation of the magnetization modulus. An unpredicted damping resonance and a dissipation regime associated with the existence of horizontal Bloch lines are also revealed.
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Submitted 1 August, 2008;
originally announced August 2008.
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Strain-Control of the magnetic anisotropy in (Ga,Mn)(As,P) ferromagnetic semiconductor layers
Authors:
Aristide Lemaître,
Audrey Miard,
Laurent Travers,
Olivia Mauguin,
Ludovic Largeau,
Catherine Gourdon,
Vincent Jeudy,
Michael Tran,
Jean-Marie George
Abstract:
A small fraction of phosphorus (up to 10 %) was incorporated in ferromagnetic (Ga,Mn)As epilayers grown on a GaAs substrate. P incorporation allows reducing the epitaxial strain or even change its sign, resulting in strong modifications of the magnetic anisotropy. In particular a reorientation of the easy axis toward the growth direction is observed for high P concentration. It offers an interes…
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A small fraction of phosphorus (up to 10 %) was incorporated in ferromagnetic (Ga,Mn)As epilayers grown on a GaAs substrate. P incorporation allows reducing the epitaxial strain or even change its sign, resulting in strong modifications of the magnetic anisotropy. In particular a reorientation of the easy axis toward the growth direction is observed for high P concentration. It offers an interesting alternative to the metamorphic approach, in particular for magnetization reversal experiments where epitaxial defects stongly affect the domain wall propagation.
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Submitted 4 July, 2008;
originally announced July 2008.
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Determination of the micromagnetic parameters in (Ga,Mn)As using domain theory
Authors:
Catherine Gourdon,
Alexandre Dourlat,
Vincent Jeudy,
Khashayar Khazen,
Hans Jürgen Von Bardeleben,
Laura Thevenard,
Aristide Lemaître
Abstract:
The magnetic domain structure and magnetic properties of a ferromagnetic (Ga,Mn)As epilayer with perpendicular magnetic easy-axis are investigated. We show that, despite strong hysteresis, domain theory at thermodynamical equilibrium can be used to determine the micromagnetic parameters. Combining magneto-optical Kerr microscopy, magnetometry and ferromagnetic resonance measurements, we obtain t…
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The magnetic domain structure and magnetic properties of a ferromagnetic (Ga,Mn)As epilayer with perpendicular magnetic easy-axis are investigated. We show that, despite strong hysteresis, domain theory at thermodynamical equilibrium can be used to determine the micromagnetic parameters. Combining magneto-optical Kerr microscopy, magnetometry and ferromagnetic resonance measurements, we obtain the characteristic parameter for magnetic domains $λ_c$, the domain wall width and specific energy, and the spin stiffness constant as a function of temperature. The nucleation barrier for magnetization reversal and the Walker breakdown velocity for field-driven domain wall propagation are also estimated.
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Submitted 2 October, 2007;
originally announced October 2007.
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Instability driven formation of domains in the intermediate state of type-I superconductors
Authors:
Vincent Jeudy,
Catherine Gourdon
Abstract:
The formation of normal-state domains in type-I superconducting indium films is investigated using the high resolution magneto-optical imaging technique. The observed patterns consist of coexisting circular and lamellar normal-phase domains surrounded by the superconducting phase. The distribution of domain surface areas is found to exhibit a threshold, above which only the lamellar shape is obs…
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The formation of normal-state domains in type-I superconducting indium films is investigated using the high resolution magneto-optical imaging technique. The observed patterns consist of coexisting circular and lamellar normal-phase domains surrounded by the superconducting phase. The distribution of domain surface areas is found to exhibit a threshold, above which only the lamellar shape is observed. We show that this threshold coincides with the predicted critical surface area for the elongation instability of the circular shape. The partition of the normal phase into circular and lamellar domains is determined by the combined effects of the elongation instability and the penetration of magnetic flux by bursts at the early stage of pattern formation. It is not governed by mutual interactions between domains, as usually assumed for self-organized systems.
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Submitted 30 March, 2006;
originally announced March 2006.
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Nucleation and Collapse of the Superconducting Phase in Type-I Superconducting Films
Authors:
Catherine Gourdon,
Vincent Jeudy,
Andrejs Cebers
Abstract:
The phase transition between the intermediate and normal states in type-I superconducting films is investigated using magneto-optical imaging. Magnetic hysteresis with different transition fields for collapse and nucleation of superconducting domains is found. This is accompanied by topological hysteresis characterized by the collapse of circular domains and the appearance of lamellar domains. M…
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The phase transition between the intermediate and normal states in type-I superconducting films is investigated using magneto-optical imaging. Magnetic hysteresis with different transition fields for collapse and nucleation of superconducting domains is found. This is accompanied by topological hysteresis characterized by the collapse of circular domains and the appearance of lamellar domains. Magnetic hysteresis is shown to arise from supercooled and superheated states. Domain-shape instability resulting from long-range magnetic interaction accounts well for topological hysteresis. Connection with similar effects in systems with long-range magnetic interactions is emphasized.
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Submitted 3 November, 2005;
originally announced November 2005.
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Impeded Growth of Magnetic Flux Bubbles in the Intermediate State Pattern of Type I Superconductors
Authors:
Vincent Jeudy,
Catherine Gourdon,
Takanori Okada
Abstract:
Normal state bubble patterns in Type I superconducting Indium and Lead slabs are studied by the high resolution magneto-optical imaging technique. The size of bubbles is found to be almost independent of the long-range interaction between the normal state domains. Under bubble diameter and slab thickness proper scaling, the results gather onto a single master curve. On this basis, in the framewo…
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Normal state bubble patterns in Type I superconducting Indium and Lead slabs are studied by the high resolution magneto-optical imaging technique. The size of bubbles is found to be almost independent of the long-range interaction between the normal state domains. Under bubble diameter and slab thickness proper scaling, the results gather onto a single master curve. On this basis, in the framework of the "current-loop" model [R.E. Goldstein, D.P. Jackson and A.T. Dorsey, Phys. Rev. Lett. 76, 3818 (1996)], we calculate the equilibrium diameter of an isolated bubble resulting from the competition between the Biot-and-Savart interaction of the Meissner current encircling the bubble and the superconductor-normal interface energy. A good quantitative agreement with the master curve is found over two decades of the magnetic Bond number. The isolation of each bubble in the superconducting matrix and the existence of a positive interface energy are shown to preclude any continuous size variation of the bubbles after their formation, contrary to the prediction of mean-field models.
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Submitted 10 June, 2005;
originally announced June 2005.
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Beta Irradiation of a Geometrically Metastable Superconducting Strip Detector with a Magnetic Flux Penetration Read-Out
Authors:
V. Jeudy,
D. Limagne,
G. Waysand,
J. I. Collar,
T. A. Girard
Abstract:
Geometrical metastability, observed in superconducting type I tin flat strips, has been previously proposed as a principle for particle detection. The energy deposition of an incoming beta-particle induces the rupture of the metastability and consequently the penetration of multiquantum flux tubes into a superconducting tin strip. We present here the first absorption spectra from two beta source…
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Geometrical metastability, observed in superconducting type I tin flat strips, has been previously proposed as a principle for particle detection. The energy deposition of an incoming beta-particle induces the rupture of the metastability and consequently the penetration of multiquantum flux tubes into a superconducting tin strip. We present here the first absorption spectra from two beta sources, which demonstrate the linearity and energy-resolution of these detectors (presented at the 6th International Workshop on Low Temperature Detectors for Dark Matter and Neutrinos (LTD-6), Interlaken, Switzerland, Sept. 1995)
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Submitted 10 December, 1995;
originally announced December 1995.
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S-35 Beta Irradiation of a Tin Strip in a State of Superconducting Geometrical Metastability
Authors:
V. Jeudy,
J. I. Collar,
T. A. Girard,
D. Limagne,
G. Waysand
Abstract:
We report the first energy loss spectrum obtained with a geometrically metastable type I superconducting tin strip irradiated by the beta-emission of S-35. (Nucl. Instr. Meth. A, in press)
We report the first energy loss spectrum obtained with a geometrically metastable type I superconducting tin strip irradiated by the beta-emission of S-35. (Nucl. Instr. Meth. A, in press)
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Submitted 30 November, 1995;
originally announced November 1995.