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Terahertz spin-current transparency through rough interfaces
Authors:
Jiří Jechumtál,
Jakub Zázvorka,
Ondřej Novák,
Martin Rejhon,
Peter Kubaščík,
Lukáš Nowak,
Petr Němec,
Eva Schmoranzerová,
Martin Veis,
Lukáš Nádvorník,
Zdeněk Kašpar
Abstract:
Spin transport across interfaces is critical for spintronic devices, yet remains difficult to probe on ultrafast timescales. We use terahertz emission spectroscopy on Co|Pt heterostructures whose interface roughness is tuned through the thickness of an underlying Au buffer layer, while leaving other growth parameters unchanged. From the measured THz electric field, we extract the interface spin-cu…
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Spin transport across interfaces is critical for spintronic devices, yet remains difficult to probe on ultrafast timescales. We use terahertz emission spectroscopy on Co|Pt heterostructures whose interface roughness is tuned through the thickness of an underlying Au buffer layer, while leaving other growth parameters unchanged. From the measured THz electric field, we extract the interface spin-current transparency ts after correcting for the changes in sample impedance and optical absorption of the stack. Surprisingly, we find that ts decreases by only approximately 30% as the interface root-mean-square roughness and the lateral grain size both increase by a factor of three, with no measurable change in the THz spectrum. These results demonstrate that interfacial spin transport is relatively robust against morphological variations on ultrafast timescales, establishing terahertz emission spectroscopy as a reliable probe of spin dynamics across imperfect interfaces.
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Submitted 26 May, 2026;
originally announced May 2026.
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Coherent control of photomagnetic back-switching by double-pump laser pulses
Authors:
T. Zalewski,
L. Nowak,
A. Stupakiewicz
Abstract:
The control of nonthermal, all-optical magnetization switching under the regime with an independent state of laser polarization opens up new opportunities for ultrafast magnetic recording. Here, we investigate the photo-magnetic back-switching capabilities of the write and erase magnetic domain pattern using double-pump pulse excitations in an iron garnet film with pure cubic magnetocrystalline sy…
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The control of nonthermal, all-optical magnetization switching under the regime with an independent state of laser polarization opens up new opportunities for ultrafast magnetic recording. Here, we investigate the photo-magnetic back-switching capabilities of the write and erase magnetic domain pattern using double-pump pulse excitations in an iron garnet film with pure cubic magnetocrystalline symmetry. It is essential to note that forward and backward magnetization switching is achievable in two distinctive scenarios: using identical linearly polarized laser pulses and with pulses having orthogonal polarization planes. By observing the switch of magnetization at domains independent of the initial state, one can nonthermally toggle the magnetization, equivalent to XOR logical operation, at frequencies reaching up to 50 GHz.
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Submitted 29 November, 2023; v1 submitted 27 November, 2023;
originally announced November 2023.
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Optical, magneto-optical properties and fiber-drawing ability of tellurite glasses in the TeO2-ZnO-BaO ternary system
Authors:
J. Hrabovsky,
L. Strizik,
F. Desevedavy,
S. Tazlaru,
M. Kucera,
L. Nowak,
R. Krystufek,
J. Mistrik,
V. Dedic,
V. Kopecky Jr.,
G. Gadret,
T. Wagner,
F. Smektala,
M. Veis
Abstract:
The presented work is focused on the optical and magneto-optical characterization of TeO2-ZnO-BaO (TZB) tellurite glasses. We investigated the refractive index and extinction coefficient dispersion by spectroscopic ellipsometry from ultraviolet, 0.193 um, up to mid infrared, 25 um spectral region. Studied glasses exhibited large values of linear (n632 = 1.91-2.09) and non-linear refractive index (…
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The presented work is focused on the optical and magneto-optical characterization of TeO2-ZnO-BaO (TZB) tellurite glasses. We investigated the refractive index and extinction coefficient dispersion by spectroscopic ellipsometry from ultraviolet, 0.193 um, up to mid infrared, 25 um spectral region. Studied glasses exhibited large values of linear (n632 = 1.91-2.09) and non-linear refractive index (n2 = 1.20-2.67x10-11 esu), Verdet constant (V632 = 22-33 radT-1m-1) and optical band gap energy (Eg = 3.7-4.1 eV). The materials characterization revealed that BaO substitution by ZnO leads (at constant content of TeO2) to an increase in linear and nonlinear refractive index as well as Verdet constant while the optical band gap energy decreases. Fiber drawing ability of TeO2-ZnO-BaO glassy system has been demonstrated on 60TeO2-20ZnO-20BaO glass with presented mid infrared attenuation coefficient. Specific parameters such as dispersion and single oscillator energy, Abbe number, and first-/ third-order optical susceptibility are enclosed together with the values of magneto-optic anomaly derived from the calculation of measured dispersion of the refractive index.
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Submitted 2 August, 2023;
originally announced August 2023.
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Magnetic properties of cobalt ultrathin film structures controlled by buffer layer roughness
Authors:
Carlos H. Verbeno,
Jakub Zázvorka,
Lukáš Nowak,
Martin Veis
Abstract:
Growth optimization of multilayers is a topic of interest due to their unique physical properties. Systems containing magnetic materials, such as platinum-cobalt, have been studied because of their potential for technological applications, e.g. spintronics, magnetic storage and magnetic sensors. Since the magnetic properties of thin layers are strongly related to the growth parameters, the fine tu…
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Growth optimization of multilayers is a topic of interest due to their unique physical properties. Systems containing magnetic materials, such as platinum-cobalt, have been studied because of their potential for technological applications, e.g. spintronics, magnetic storage and magnetic sensors. Since the magnetic properties of thin layers are strongly related to the growth parameters, the fine tuning of these parameters is necessary to produce multilayers with specific properties required in various applications. Here, an efficient approach to tune the coercive field of Co ultrathin films in the multilayer by varying the underlayer thickness is demonstrated. Using magnetron sputtering, we prepared multilayer systems of Au(x)/Pt(5nm)/Co(0.7nm)/Au(5nm) with various thicknesses of Au underlayer. The surface morphology of Au(x)/Pt(5nm) stack on which Co layer was deposited was studied by atomic force microscopy. We show the possibility to control the interfacial roughness by changing the Au underlayer thickness due to its island-like growth mechanism (Volmer-Weber mode). As the nominal thickness of Au increases, the islands grow in larger lateral size, resulting in a higher overall roughness of the layer surface. Magnetization measurements indicate a direct influence of the underlayer roughness on the coercivity of the multilayers by promoting additional magnetic anisotropy. With thickness of the Au layer up to 20 nm, we can change the coercive field in the range from ~200 Oe to ~1100 Oe, while remaining a nearly constant saturation magnetization. The use of Cu replacing Au underlayer in the same multilayers was also investigated, demonstrating the possibility of coercivity adjustment using different materials. The results are important for applications where the magnetic properties of multilayer structures based on Co thin films could be adjusted via buffer layer roughness engineering.
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Submitted 27 March, 2023;
originally announced March 2023.