arXiv subjects

E. Schmoranzerova

Publications and source records attributed to E. Schmoranzerova.

10 recordsLinked to original sources

arXiv2026

Disentangling magnetic and optical contributions in ultrafast dynamics of antiperovskite non-collinear antiferromagnets

Non-collinear antiferromagnets are a class of spin-polarized antiferromagnets in which chiral spin textures give rise to Berry-curvature-driven phenomena, such as the anomalous Hall effect (AHE), without net magnetization. We investigate the properties of thin films of antiperovskite non-collinear antiferromagnetic metals Mn3NiN and Mn3GaN using pump-probe experiments. In both materials, we observe a strong dependence of pump-polarization-independent dynamics, induced by femtosecond laser pulses, on the angle between the sample normal and the direction of probe propagation. In Mn3NiN, where the presence of a sizable AHE indicates the Γ4g phase, the measured magnetooptical (MO) signals acquire an additional, strong dependence on the external magnetic field when the probe pulses are incident at nonzero angles. In contrast, in Mn3GaN, where the absence of AHE indicates the Γ5g phase, the measured signals do not depend on the magnetic field. Using probe-polarization-resolved measurements combined with full optical modeling based on Yeh's formalism, we quantitatively separate magnetic and non-magnetic contributions to the measured signals. We show that in Mn3NiN, the observed magnetic field dependence results from field-controlled redistribution of magnetic domain populations, enabled by their piezomagnetic moments and detected by a Kerr-like MO effect, while this effect is absent in Mn3GaN. Temperature-dependent measurements reveal a change from single-step to two-step quenching dynamics with increasing temperature in Mn3NiN. This behavior contrasts with the nearly temperature-independent quenching dynamics reported for the non-collinear antiferromagnetic Heusler compound Mn3Sn, but resembles the crossover from type-I to type-II demagnetization dynamics in metallic ferromagnets.

cond-mat.mtrl-sci↗

arXiv2026

Spin-to-charge-current conversion in altermagnetic candidate RuO$_2$ probed by terahertz emission spectroscopy

Using the THz emission spectroscopy, we investigate ultrafast spin-to-charge current conversion in epitaxial thin films of the altermagnetic candidate RuO$_2$. We perform a quantitative analysis of competing effects that can contribute to the measured anisotropic THz emission. These include the anisotropic inverse spin splitter and spin Hall effects in RuO$_2$, the anisotropic conductivity of RuO$_2$, and the birefringence of the TiO$_2$ substrate. We observe that the leading contribution to the measured signals comes from the anisotropic inverse spin Hall effect, with an average spin-Hall angle of $2.4\times 10^{-3}$ at room temperature. In comparison, a possible contribution from the altermagnetic inverse spin-splitter effect is found to be approximately $2-4\times 10^{-4}$. Our work stresses the importance of carefully disentangling spin-dependent phenomena that can be generated by the unconventional altermagnetic order, from the effects of the relativistic spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2026

Ultrafast control of spin order by linearly polarized light in noncollinear antiferromagnetic metals

The non-thermal optical control of magnetic order offers a promising route to ultrafast, energy-efficient information technologies. Although optical manipulation of magnetism in metals has been extensively studied, experimentally demonstrated effects have so far been limited to heat-driven dynamics or helicity-dependent mechanisms. Here, we report ultrafast non-thermal control of spin order in noncollinear antiferromagnetic Mn-based antiperovskite nitrides Mn3NiN and Mn3GaN, driven solely by the polarization orientation of linearly polarized femtosecond laser pulses. Using time-resolved magneto-optical pump-probe experiments based on the Voigt effect, we observe sub-picosecond changes in magnetic order followed by picosecond relaxation. The magneto-optical response depends on the relative orientation of the pump and probe polarization planes, with linear-polarization dependence reaching up to 95%, a value unprecedented in metallic magnets. This phenomenon is observed in two different materials and persists over a wide range of excitation wavelengths, fluences, and temperatures, demonstrating its robustness. Symmetry analysis and microscopic modeling indicate that optically induced torques alone cannot fully explain the observed dynamics. We therefore propose laser-induced formation of transient spin-spiral states as a possible excitation mechanism.

cond-mat.mtrl-sci↗

arXiv2025

Exploring the impact of the inverse Faraday effect on all-optical helicity-dependent magnetization switching

All-optical helicity-dependent magnetization switching (AO-HDS) is the quickest data recording technique using only ultrashort laser pulses. FePt grains provide an ideal platform for examining the interaction of effects conducting magnetization switching. We identify the magnetic circular dichroism (MCD) and the inverse Faraday effect (IFE) as the primary switching forces. Ultrafast photon absorption rapidly elevates electron temperatures, quenching magnetization. The MCD's helicity-dependent absorption ensures distinct electron temperatures, holding a finite switching probability by generating different spin noise rates in each spin channel. The IFE induces a magnetic moment, enhancing this probability. We present ultrashort laser pulse (<200 fs) AO-HDS experiments in the near-infrared spectral range from 800 nm to 1500 nm, demonstrating a correlation between switching efficiency and absorbed energy density. Elevating electron temperatures to the Curie point enables the IFE to induce a magnetic moment for deterministic switching in the quenched magnetization state. Unlike in films or multilayers, where domain wall motion and domain growth govern the switching process, increasing the MCD in nanometer-sized grains does not enhance switching efficiency. Electrons around the Curie temperature typically reach increased switching rates for higher induced magnetization generated by the IFE. The MCD sets the necessary switching condition, separating electron temperatures. The IFE generates a magnetic moment, directing spins toward the desired orientation and improving switching efficiency. Every laser pulse initiates a new switching probability for each grain, increasing the role of direction indication by the IFE. Stronger absorption assures higher induced magnetization at low switching fluences.

physics.app-ph↗

arXiv2022

Ultrashort spin-orbit torque generated by femtosecond laser pulses

To realize the very objective of spintronics, namely the development of ultra-high frequency and energy-efficient electronic devices, an ultrafast and scalable approach to switch magnetic bits is required. Magnetization switching with spin currents generated by the spin-orbit interaction at ferromagnetic/non-magnetic interfaces is one of such scalable approaches, where the ultimate switching speed is limited by the Larmor precession frequency. Understanding the magnetization precession dynamics induced by spin-orbit torques (SOTs) is therefore of great importance. Here we demonstrate generation of ultrashort SOT pulses that excite Larmor precession at an epitaxial Fe/GaAs interface by converting femtosecond laser pulses into high-amplitude current pulses in an electrically biased p-i-n photodiode. We control the polarity, amplitude, and duration of the current pulses and, most importantly, also their propagation direction with respect to the crystal orientation. The SOT origin of the excited Larmor precession was revealed by a detailed analysis of the precession phase and amplitude at different experimental conditions.

cond-mat.mtrl-sci↗

arXiv2022

Circular photogalvanic effects in topological insulator/ferromagnet hybrid structures

We study laser driven spin-current effects at ferromagnet/topological-insulator interfaces by two complementary experimental approaches. The DC photocurrent is studied in ferromagnet/topological-insulator bilayers with high spatial resolution. Dynamic interface currents are explored via the emission of terahertz radiation emitted by these currents with high temporal resolution. From our experiments, we reveal a lateral and dynamic interaction of the ferromagnet and the topological insulator interface.

cond-mat.mes-hall↗

arXiv2020

Quasi-nondegenerate pump-probe magnetooptical experiment in GaAs/AlGaAs heterostructure based on spectral filtration

We report on a quasi-nondegenerate pump-probe technique that is based on spectral-filtration of femtosecond laser pulses by a pair of mutually-spectrally-disjunctive interference filters. This cost- and space-efficient approach can be used even in pump-probe microscopy where collinear propagation of pump and probe pulses is dictated by utilization of a microscopic objective. This technique solves the contradictory requirements on an efficient removal of pump photons from the probe beam, to achieve a good signal-to-noise ratio, simultaneously with a needed spectral proximity of the excitation and probing, which is essential for magnetooptical study of many material systems. Importantly, this spectral-filtration of 100 fs long laser pulses does not affect considerably the resulting time-resolution, which remains well below 500 fs. We demonstrate the practical applicability of this technique with close but distinct wavelengths of pump and probe pulses in spatially- and time-resolved spin-sensitive magnetooptical Kerr effect (MOKE) experiment in GaAs/AlGaAs heterostructure, where a high-mobility spin system is formed after optical injection of electrons at wavelengths close to MOKE resonance. In particular, we studied the time- and spatial-evolutions of charge-related (reflectivity) and spin-related (MOKE) signals. We revealed that they evolve in a similar but not exactly the same way which we attributed to interplay of several electron many-body effects in GaAs.

cond-mat.mtrl-sci↗

arXiv2018

Observation of spin Nernst photocurrents in topological insulators

The theoretical prediction of topological insulators in 2007 triggered tremendous interest. They are of fundamental interest because of their topological twist in k-space, which comes along with unidirectional, spin-polarized surface-state currents, required for spin-optoelectronics. This property makes topological insulators on one hand perfect materials for optically generated, ultrafast spin-bunches spin-current sources for the generation of THz radiation. On the other hand, those spin-polarized surface-state currents when generated by a voltage lead to large spin Hall effects, or when generated by a temperature gradient to the thermal analogue, the spin Nernst effect. Both mutually convert charge/ heat currents into transverse spin currents leading to spin accumulations. By connecting both research fields, we show the evidence of heat-transport related spin Hall effects that can be extracted from opto-transport experiments. This heat-driven spin Nernst effect drives a transverse spin-current and affects the optical spin-orientation in the three-dimensional topological insulator. This manifests as a modification of the circular polarization-dependent photocurrent. We illuminate the detailed thermocurrent distribution, including the influence of edges and contacts, in spatially resolved current maps.

cond-mat.mes-hall↗

arXiv2018

Voigt effect-based wide-field magneto-optical microscope integrated in a pump-probe experimental setup

In this work we describe an experimental setup for spatially-resolved pump-probe experiment with integrated wide-field magneto-optical (MO) microscope. The MO microscope can be used to study ferromagnetic materials with both perpendicular-to-plane and in-plane magnetic anisotropy via polar Kerr and Voigt effects, respectively. The functionality of the Voigt effect-based microscope was tested using an in-plane magnetized ferromagnetic semiconductor (Ga,Mn)As. It was revealed that the presence of mechanical defects in the (Ga,Mn)As epilayer alters significantly the magnetic anisotropy in their proximity. The importance of MO experiments with simultaneous temporal and spatial resolutions was demonstrated using (Ga,Mn)As sample attached to a piezoelectric actuator, which produces a voltage-controlled strain. We observed a considerably different behavior in different parts of the sample that enabled us to identify sample parts where the epilayer magnetic anisotropy was significantly modified by a presence of the piezostressor and where it was not. Finally, we discuss the possible applicability of our experimental setup for the research of compensated antiferromagnets, where only MO effects even in magnetic moments are present.

cond-mat.mtrl-sci↗

arXiv2014

Comparison of micromagnetic parameters of ferromagnetic semiconductors (Ga,Mn)(As,P) and (Ga,Mn)As

We report on the determination of micromagnetic parameters of epilayers of the ferromagnetic semiconductor (Ga,Mn)As, which has easy axis in the sample plane, and (Ga,Mn)(As,P) which has easy axis perpendicular to the sample plane. We use an optical analog of ferromagnetic resonance where the laser-pulse-induced precession of magnetization is measured directly in the time domain. By the analysis of a single set of pump-and-probe magneto-optical data we determined the magnetic anisotropy fields, the spin stiffness and the Gilbert damping constant in these two materials. We show that incorporation of 10% of phosphorus in (Ga,Mn)As with 6% of manganese leads not only to the expected sign change of the perpendicular to plane anisotropy field but also to an increase of the Gilbert damping and to a reduction of the spin stiffness. The observed changes in the micromagnetic parameters upon incorporating P in (Ga,Mn)As are consistent with the reduced hole density, conductivity, and Curie temperature of the (Ga,Mn)(As,P) material. We report that the magnetization precession damping is stronger for the n = 1 spin wave resonance mode than for the n = 0 uniform magnetization precession mode.

cond-mat.mtrl-sci↗