arXiv subjects

I. Yu. Pashenkin

Publications and source records attributed to I. Yu. Pashenkin.

4 recordsLinked to original sources

arXiv2024

Magneto-optical Control of Ordering Kinetics and Vacancy Behavior in Fe-Al Thin Films Quenched by Laser

One of issues arising in materials science is a behavior of non-equilibrium point defects in the atomic lattice, which defines the rates of chemical reactions and relaxation processes as well as affects the physical properties of solids. It is previously theoretically predicted that melting and rapid solidification of metals and alloys provides a vacancy concentration in the quenched material, which can be comparable to that quantity at the point of melting. Here, the vacancy behavior is studied exerimentally in thin films of the near equiatomic Fe-Al alloy subjected to nanosecond laser annealing with intensities up to film ablation. The effects of laser irradiation are studied by monitoring magneto-optically the ordering kinetics in the alloy at the very ablation edge, within a narrow (micron-scale) ring-shaped region around the ablation zone. Quantitatively, the vacancy supersaturation in the quenched alloy has been estimated by fitting a simulated temporal evolution of the long-range chemical order to the obtained experimental data. Laser quenching (LQ) of alloys and single-element materials would be a tool for obtaining novel phase states within a small volume of the crystal.

cond-mat.mtrl-sci↗

arXiv2023

Finite momentum superconductivity in superconducting hybrids: Orbital mechanism

Normally in superconductors, as in conductors, in the state with zero current $I$ the momentum of superconducting electrons $\hbar q =0$. Here we demonstrate theoretically and present experimental evidences that in superconducting/normal metal (SN) hybrid strip placed in in-plane magnetic field $B_{in}$ finite momentum state ($\hbar q \neq 0$) is realized when $I=0$. This state is characterized by current-momentum dependence $I(q)\neq -I(-q)$, nonreciprocal kinetic inductance $L_k(I) \neq L_k(-I)$ and different values of depairing currents $I_{dep}^{\pm}$ flowing along the SN strip in opposite directions. Found properties have {\it orbital} nature and are originated from gradient of density of superconducting electrons $\nabla n$ across the thickness of SN strip and field induced Meissner currents. We argue that this type of finite momentum state should be rather general phenomena in superconducting structures with artificial or intrinsic inhomogeneities.

cond-mat.supr-con↗

arXiv2022

Extrinsic tunnel Hall effect in CoFeB/MgO/Pt junctions

The Hall effect that occurs when current flows through a CoFeB/MgO/Pt tunnel junction is investigated. It is shown that the transverse voltage in Pt electrode is nonlinear on a DC voltage applied to the tunnel junction. It has both linear (odd) and quadratic (even) parts. The linear part contains well-known contributions of the anomalous Hall effect in the ferromagnetic electrode, inverse spin-hall effect in platinum and others. The quadratic part is a phenomenon caused by the spin-orbit scattering of electrons in an external electric field induced by a voltage applied to the barrier. This field reaches values of $10^9$ V/m which is close to internal atomic fields. The magnitude of both effects decreases as thickness of Pt electrode is increased due to shunting effects.

cond-mat.other↗

arXiv2021

Voltage controllable superconducting state in the multi-terminal superconductor-normal metal bridge

We study voltage controllable superconducting state in multi-terminal bridge composed of the dirty superconductor/pure normal metal (SN) bilayer and pure normal metal. In the proposed system small control current $I_{ctrl}$ flows via normal bridge, creates voltage drop $V$ and modifies distribution function of electrons in connected SN bilayer. In case of long normal bridge the voltage induced nonequilibrium effects could be interpreted in terms of increased local electron temperature. In this limit we experimentally find large sensitivity of critical curent $I_c$ of Cu/MoN/Pt-Cu bridge to $I_{ctrl}$ and relatively large current gain which originate from steep dependence of $I_c$ on temperature and large $I_c$ (comparable with theoretical depairing current of superconducting bridge). In the short normal bridge deviation from equilibrium cannot be described by simple increase of local temperature but we also theoretically find large sensitivity of $I_c$ to control current/voltage. In this limit we predict existence at finite $V$ of so called in-plane Fulde-Ferrell state with spontaneous currents in SN bilayer. We argue that its appearance is connected with voltage induced paramagnetic response in N layer.

cond-mat.supr-con↗