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Exploring Multifunctionality in MgO-Based Magnetic Tunnel Junctions with Coexisting Magnetoresistance and Memristive Properties
Authors:
Alejandro Schulman,
Elvira Paz,
Tim Böhnert,
Alex Steven Jenkins,
Ricardo Ferreira
Abstract:
Magnetic tunnel junctions (MTJs) and memristors are two key emerging nanotechnologies that attracted significant interest for potential applications at the forefront of the digital revolution, including sensing, data storage, and non-conventional computation. The co-integration of these phenomena into a single multifunctional device is an important step toward harnessing the re-programmability of…
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Magnetic tunnel junctions (MTJs) and memristors are two key emerging nanotechnologies that attracted significant interest for potential applications at the forefront of the digital revolution, including sensing, data storage, and non-conventional computation. The co-integration of these phenomena into a single multifunctional device is an important step toward harnessing the re-programmability of memristive systems with the high yield and varied functionality of MTJs. This study demonstrates the co-existence of magnetoresistance and memristive properties on MgO-based MTJs. These devices show a magnetoresistance with a linear response as a function of a magnetic field and no hysteresis, which are the requirements for good magnetic field sensors, as well as demonstrating a non-volatile and quasi-analogue memristive behavior as a function of an applied electrical field down to nanosecond pulses. Furthermore, by doping the oxide barrier, the memristive power consumption is lowered by 20% giving the multi-functionality of the devices a promising scalability potential. This study also shows that, memristive switching can be reversibly used to completely suppress and recover the spintronic functionalities. These results can pave the way for a seamless co-integration of memristors and spintronic devices in complex reprogrammable circuits addressing applications such as reprogrammable multifunctional field sensor arrays and neuromorphic computing.
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Submitted 22 July, 2026;
originally announced July 2026.
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The impact of local pinning sites in magnetic tunnel junctions with non-homogeneous free layers
Authors:
Alex. S. Jenkins,
Leandro Martins,
Luana Benetti,
Alejandro Schulman,
Pedro Anacleto,
Marcel Claro,
Elvira Paz,
Ihsan Çaha,
Francis Leonard Deepak,
Ricardo Ferreira
Abstract:
Pinning at local defects is a significant road block for the successful implementation of technological paradigms which rely on the dynamic properties of non-trivial magnetic textures. In this report a comprehensive study of the influence of local pinning sites for non-homogeneous magnetic layers integrated as the free layer of a magnetic tunnel junction is presented, both experimentally and with…
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Pinning at local defects is a significant road block for the successful implementation of technological paradigms which rely on the dynamic properties of non-trivial magnetic textures. In this report a comprehensive study of the influence of local pinning sites for non-homogeneous magnetic layers integrated as the free layer of a magnetic tunnel junction is presented, both experimentally and with corresponding micromagnetic simulations. The pinning sites are found to be extremely detrimental to the frequency controllability of the devices, a key requirement for their use as synapses in a frequency multiplexed artificial neural networks. In addition to describing the impact of the local pinning sites in the more conventional NiFe, a vortex-based magnetic tunnel junction with an amorphous free layer is presented which shows significantly improved frequency selectivity, marking a clear direction for the design of future low power devices.
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Submitted 17 April, 2023;
originally announced April 2023.
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Broadband voltage rectifier induced by linear bias dependence in CoFeB/MgO magnetic tunnel junctions
Authors:
M. Tarequzzaman,
A. S. Jenkins,
T. Böhnert,
J. Borme,
L. Martins,
E. Paz,
R. Ferreira,
P. P. Freitas
Abstract:
In this paper, the perpendicular magnetic anisotropy (PMA) is tailored by changing the thickness of the free layer with the objective of producing MTJ nano-pillars with smooth linear resistance dependence with both in-plane magnetic field and DC bias. We furthermore demonstrate how this linear bias dependence can be used to create a zero-threshold broadband voltage rectifier, a feature which is im…
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In this paper, the perpendicular magnetic anisotropy (PMA) is tailored by changing the thickness of the free layer with the objective of producing MTJ nano-pillars with smooth linear resistance dependence with both in-plane magnetic field and DC bias. We furthermore demonstrate how this linear bias dependence can be used to create a zero-threshold broadband voltage rectifier, a feature which is important for rectification in wireless charging and energy harvesting applications. By carefully balancing the amount of PMA acting in the free layer the measured RF to DC voltage conversion efficiency can be made as large as 11%.
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Submitted 11 April, 2018;
originally announced April 2018.
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Magnetic oscillations Excited by Concurrent Spin Injection from a Tunneling Current and a Spin Hall Current
Authors:
M. Tarequzzaman,
T. Böhnert,
M. Decker,
J. D. Costa,
J. Borme,
B. Lacoste,
E. Paz,
A. S. Jenkins,
S. Serrano-Guisan,
C. H. Back,
R. Ferreira,
P. P. Freitas
Abstract:
In this paper, a 3-terminal spin-transfer torque nano-oscillator (STNO) is studied using the concurrent spin injection of a spin-polarized tunneling current and a spin Hall current exciting the free layer into dynamic regimes beyond what is achieved by each individual mechanism. The pure spin injection is capable of inducing oscillations in the absence of charge currents effectively reducing the c…
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In this paper, a 3-terminal spin-transfer torque nano-oscillator (STNO) is studied using the concurrent spin injection of a spin-polarized tunneling current and a spin Hall current exciting the free layer into dynamic regimes beyond what is achieved by each individual mechanism. The pure spin injection is capable of inducing oscillations in the absence of charge currents effectively reducing the critical tunneling current to zero. This reduction of the critical charge currents can improve the endurance of both STNOs and non-volatile magnetic memories (MRAM) devices. It is shown that the system response can be described in terms of an injected spin current density $J_s$ which results from the contribution of both spin injection mechanisms, with the tunneling current polarization $p$ and the spin Hall angle $θ$ acting as key parameters determining the efficiency of each injection mechanism. The experimental data exhibits an excellent agreement with this model which can be used to quantitatively predict the critical points ($J_s = -2.26\pm 0.09 \times 10^9 \hbar/e$ A/m$^2$) and the oscillation amplitude as a function of the input currents. In addition, the fitting of the data also allows an independent confirmation of the values estimated for the spin Hall angle and tunneling current polarization as well as the extraction of the damping $α= 0.01$ and non-linear damping $Q = 3.8\pm 0.3$ parameters.
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Submitted 6 February, 2018;
originally announced February 2018.
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Femtosecond control of electric currents at the interfaces of metallic ferromagnetic heterostructures
Authors:
T. J. Huisman,
R. V. Mikhaylovskiy,
J. D. Costa,
F. Freimuth,
E. Paz,
J. Ventura,
P. P. Freitas,
S. Blügel,
Y. Mokrousov,
Th. Rasing,
A. V. Kimel
Abstract:
The idea to utilize not only the charge but also the spin of electrons in the operation of electronic devices has led to the development of spintronics, causing a revolution in how information is stored and processed. A novel advancement would be to develop ultrafast spintronics using femtosecond laser pulses. Employing terahertz (10$^{12}$ Hz) emission spectroscopy, we demonstrate optical generat…
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The idea to utilize not only the charge but also the spin of electrons in the operation of electronic devices has led to the development of spintronics, causing a revolution in how information is stored and processed. A novel advancement would be to develop ultrafast spintronics using femtosecond laser pulses. Employing terahertz (10$^{12}$ Hz) emission spectroscopy, we demonstrate optical generation of spin-polarized electric currents at the interfaces of metallic ferromagnetic heterostructures at the femtosecond timescale. The direction of the photocurrent is controlled by the helicity of the circularly polarized light. These results open up new opportunities for realizing spintronics in the unprecedented terahertz regime and provide new insights in all-optical control of magnetism.
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Submitted 12 May, 2015;
originally announced May 2015.
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Towards wafer scale inductive characterization of spin transfer torque critical current density of magnetic tunnel junction stacks
Authors:
Sibylle Sievers,
Niklas Liebing,
Santiago Serrano-Guisan,
Ricardo Ferreira,
Elvira Paz,
Ambra Caprile,
Alessandra Manzin,
Massimo Pasquale,
Witold Skowroński,
Tomasz Stobiecki,
Karsten Rott,
Günter Reiss,
Jürgen Langer,
Berthold Ocker,
Hans Werner Schumacher
Abstract:
We explore the prospects of wafer scale inductive probing of the critical current density $j^{c0}$ for spin transfer torque switching of a CoFeB/MgO/CoFeB magnetic tunnel junction with varying MgO thickness. From inductive measurements magnetostatic parameters and the effective damping are derived and $j^{c0}$ is calculated based on spin transfer torque equations. The inductive values compare well…
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We explore the prospects of wafer scale inductive probing of the critical current density $j^{c0}$ for spin transfer torque switching of a CoFeB/MgO/CoFeB magnetic tunnel junction with varying MgO thickness. From inductive measurements magnetostatic parameters and the effective damping are derived and $j^{c0}$ is calculated based on spin transfer torque equations. The inductive values compare well to the values derived from current induced switching measurements on individual nanopillars. Using a wafer scale inductive probe head could in the future enable wafer probe station based metrology of $j^{c0}$.
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Submitted 18 November, 2014;
originally announced November 2014.