arXiv subjects

Olga N. Miroshkina

Publications and source records attributed to Olga N. Miroshkina.

6 recordsLinked to original sources

arXiv2026

Modelling the dynamics of the martensitic transformation in Ni$_2$MnGa with machine-learning force-fields

The martensitic transformations in stoichiometric Ni$_2$MnGa and related Heusler alloys are governed by a delicate interplay between electronic structure, magnetism, and lattice dynamics. While density functional theory (DFT) has successfully mapped the energy landscape of modulated martensites, it remains computationally prohibitive for capturing finite-temperature dynamics across relevant length and time scales. Here, we bridge this gap by constructing DFT-trained machine-learning force-fields (ML-FF) interpolated from ab initio molecular dynamics. We demonstrate that ML-FF trained on DFT data can reproduce key features of Ni$_2$MnGa, including the soft TA$_2$ phonon and a preference for nanotwinned martensites. Using classical molecular dynamics simulations, we explore the impact of adaptive nanotwinning on the austenite-martensite transition, which facilitates the dynamics of both, forward and backward transformation. We demonstrate, that the negative twin boundary energy along the entire transformations path predicted by DFT for $T=0$, supports the formation of ordered modulated martensites at finite temperatures. Our results pave the way for large-scale simulations of magnetic shape memory alloys with near-DFT accuracy.

cond-mat.mtrl-sci↗

arXiv2023

Dissipation losses limiting first-order phase transition materials in cryogenic caloric cooling: A case study on all-d-metal Ni(-Co)-Mn-Ti Heusler alloys

Ni-Mn-based Heusler alloys, in particular all-d-metal Ni(-Co)-Mn-Ti, are highly promising materials for energy-efficient solid-state refrigeration as large multicaloric effects can be achieved across their magnetostructural martensitic transformation. However, no comprehensive study on the crucially important transition entropy change $Δs_t$ exists so far for Ni(-Co)-Mn-Ti. Here, we present a systematic study analyzing the composition and temperature dependence of $Δs_t$. Our results reveal a substantial structural entropy change contribution of approximately 65 J(kgK)$^{-1}$, which is compensated at lower temperatures by an increasingly negative entropy change associated with the magnetic subsystem. This leads to compensation temperatures $T_{comp}$ of 75 K and 300 K in Ni$_{35}$Co$_{15}$Mn$_{50-y}$Ti$_{y}$ and Ni$_{33}$Co$_{17}$Mn$_{50-y}$Ti$_{y}$, respectively, below which the martensitic transformations are arrested. In addition, we simultaneously measured the responses of the magnetic, structural and electronic subsystems to the temperature- and field-induced martensitic transformation near $T_{comp}$, showing an abnormal increase of hysteresis and consequently dissipation energy at cryogenic temperatures. Simultaneous measurements of magnetization and adiabatic temperature change $ΔT_{ad}$ in pulsed magnetic fields reveal a change in sign of $ΔT_{ad}$ and a substantial positive and irreversible $ΔT_{ad}$ up to 15 K at 15 K as a consequence of increased dissipation losses and decreased heat capacity. Most importantly, this phenomenon is universal, it applies to any first-order material with non-negligible hysteresis and any stimulus, effectively limiting the utilization of their caloric effects for gas liquefaction at cryogenic temperatures.

cond-mat.mtrl-sci↗

arXiv2021

Impact of local arrangement of Fe and Ni on the phase stability and magnetocrystalline anisotropy in Fe-Ni-Al Heusler alloys

On the basis of density functional calculations, we report on a comprehensive study of the influences of atomic arrangement and Ni substitution for Al on the ground state structural and magnetic properties for Fe$_2$Ni$_{1+x}$Al$_{1-x}$ Heusler alloys. We discuss systematically the competition between five Heusler-type structures formed by shuffles of Fe and Ni atoms and their thermodynamic stability. All~Ni-rich Fe$_2$Ni$_{1+x}$Al$_{1-x}$ tend to decompose into a dual-phase mixture consisting of Fe$_2$NiAl and~FeNi. The~successive replacement of Ni by Al leads to a change of ground state structure and eventually an increase in magnetocrystalline anisotropy energy~(MAE). We predict for stoichiometric Fe$_2$NiAl a ground state structure with nearly cubic lattice parameters but alternating layers of Fe and Ni possessing an uniaxial MAE which is even larger than tetragonal L1$_0$-FeNi. This opens an alternative route for improving the phase stability and magnetic properties in FeNi-based permanent magnets.

cond-mat.mtrl-sci↗

arXiv2021

Impact of local arrangement of Fe and Ni in Fe-Ni-Al Heusler alloys on the phase stability and magnetocrystalline anisotropy

On the basis of the density functional calculations in combination with the supercell approach, we report on a complete study of the influences of atomic arrangement and Ni substitution for Al on the ground state structural and magnetic properties for Fe$_2$Ni$_{1+x}$Al$_{1-x}$ Heusler alloys. We discuss systematically the competition between five cubic Heusler-type structures formed by shuffles of Fe and Ni atoms to reveal routes for improving the phase stability and magnetic properties, in particular magnetocrystalline anisotropy~(MAE). We predict that in case of Fe$_2$NiAl the ground state cubic structure with alternated layers of Fe and Ni possesses the highest uniaxial MAE which twice larger than that for the tetragonal L1$_0$ FeNi. The successive Ni doping at Al sublattice leads to a change of ground state structure and to reduce of the MAE. In addition, the phase stability against the decomposition into the stable systems at finite-temperatures is discussed. All~Ni-rich Fe$_2$Ni$_{1+x}$Al$_{1-x}$ are turned to be decomposed into a dual-phase consisting of Fe$_2$NiAl and FeNi.

cond-mat.mtrl-sci↗

arXiv2020

Superconducting and Antiferromagnetic Properties of Dual-Phase V$_3$Ga

The binary compound V$_3$Ga can exhibit two near-equilibrium phases, consisting of the A15 structure that is superconducting, and the Heusler D0$_3$ structure that is semiconducting and antiferromagnetic. Density functional theory calculations show that the two phases are closely degenerate, being separated by only ~10 meV/atom. Magnetization measurements on bulk-grown samples show superconducting behavior below 14 K. These results indicate the possibility of using V$_3$Ga for quantum technology devices utilizing both superconductivity and antiferromagnetism at the same temperature.

cond-mat.mtrl-sci↗

arXiv2020

Exchange-correlation corrections for electronic properties of half-metallic Co$_2$FeSi and nonmagnetic semiconductor CoFeTiAl

We consider two cobalt-based full-Heusler compounds CoFeTiAl and Co$_2$FeSi, for which Coulomb correlation effects play an important role. Since the standard GGA scheme does not provide a precise description of the electronic properties near the Fermi level, we use a meta-GGA functional capable to improve the description of the electronic properties of CoFeTiAl and Co$_2$FeSi. In particular, we find a better agreement with the experiment for the magnetic moment and the energy-band gap. Moreover, our calculations show that pressure enhances the insulating properties of Co$_2$FeSi and CoTiFeAl.

cond-mat.mtrl-sci↗