arXiv subjects

Soheil Ershadrad

Publications and source records attributed to Soheil Ershadrad.

13 recordsLinked to original sources

arXiv2026

Data-driven discovery and rapid, direct synthesis of MXenes

MXenes, two-dimensional transition-metal carbides and nitrides, are typically obtained from MAX phases, yet historical reports suggest a broader, largely unexplored chemical space. Here we combine machine-learning-assisted database mining with experiments to uncover overlooked multilayer (ml) MXenes. Screening of repositories reveals a "Treasure Chest" of 38 previously synthesized but unrecognized ml-MXene candidates. Guided by these findings, we rediscover five MXenes using a rapid, scalable self-propagating high-temperature synthesis that requires no sustained external heating and completes within minutes. Inspired by the identified chemistries, we further realize 11 previously unexplored rare-earth-based M2CT2 MXenes (M= Pr, Nd, Sm, Gd, Tb, Ho, and Tm). Experiments and theory reveal semiconducting behavior and diverse magnetic states across this family. Together, these results expand the MXene family and demonstrate a data-driven strategy for accelerating materials discovery through sustainable methods.

cond-mat.mtrl-sci↗

arXiv2026

Novel 2D Altermagnetic Vanadium Oxide with a Buckled Lieb Structure

Altermagnetism has recently emerged as a highly promising phase for spintronics, offering the combined advantages of both antiferromagnets and ferromagnets. Here, using a first-principles analysis based on density functional theory (DFT), we identify a monolayer V$_2$O crystal in a buckled Lieb lattice as a promising two-dimensional altermagnetic material. The structural and thermal stability of V$_2$O is verified through calculations of the crystal's formation energy, phonon structure, room-temperature ab initio molecular dynamics, and stiffness matrix. The system is found to exhibit auxetic behavior with a negative Poisson's ratio. Our calculations indicate an antiferromagnetic ground state with a local magnetic moment of $2.79\,μ_{\mathrm{B}}$ per V atom and a magnetocrystalline anisotropy that favors an out-of-plane easy axis. The electronic structure exhibits a momentum-dependent spin splitting of 1.2 eV, which is a characteristic of altermagnets. Inclusion of spin-orbit coupling breaks the symmetry of the quadratic band crossing near the Fermi level, resulting in a large Berry curvature and significant intrinsic spin Hall conductivity around $40\,(\hbar/e)\,\mathrm{S\,cm^{-1}}$. The results demonstrate that monolayer V$_2$O serves as a robust room-temperature altermagnetic platform, exhibiting magnetic anisotropy and spin-dependent transport responses.

cond-mat.mes-hall↗

arXiv2026

Generating Symmetric Materials using Latent Flow Matching

Tackling the task of materials generation, we aim to enhance the previously proposed All-atom Diffusion Transformer (ADiT) by introducing SymADiT, a symmetry-aware variant. To do so, we use a representation of materials based on Wyckoff positions. We follow ADiT and perform generative modelling in latent space, adapted to our symmetry-aware representation. By forcing the output of the generative model to adhere to the symmetry restrictions imposed by the generated crystal's space group and each atom's Wyckoff-position, the generated materials exhibit more realistic symmetry properties. We benchmark our method against both symmetry-aware and symmetry-agnostic models for materials generation and show competitive performance, generating stable, symmetric materials with a simple Transformer architecture.

cs.LG↗

arXiv2026

Tuning Structure and Magnetism in Large-Scale 2D Ferromagnet Fe$_3$GeTe$_2$ through Ni Doping

Two-dimensional ferromagnets with strong perpendicular magnetic anisotropy exhibit magnetic order down to the monolayer thickness, beneficial for energy-efficient spintronic devices. In this work, molecular beam epitaxy has been employed to realize controlled Ni-doping in Fe$_{3}$GeTe$_{2}$ (FGT) epitaxial films. MBE not only enables a large-scale growth of 2D films, but also allows a precise control over thickness and doping. X-ray diffraction and scanning transmission electron microscopy (STEM) reveal the formation of high-quality epitaxial films of pristine and Ni-doped FGT on graphene via van der Waals (vdW) epitaxy. Integrated differential phase contrast STEM images further provide in-depth information on Ni substitution and intercalation into the vdW gaps. Ni incorporation in doped films results in the shrinking of both in-plane and out-of-plane lattice parameters. Superconducting Quantum Interference Device, Hall, and X-ray magnetic circular dichroism measurements were utilized to probe the ferromagnetic properties of the films. Due to both Ni substitution and intercalation into the vdW gaps for Ni-doped FGT films, we observed a suppression of PMA and a drastic reduction in the Curie temperature down to 50 K. Our density functional theory based calculations of structural and magnetic properties further supports and provide deep insights into the variations of magnetic exchange interaction parameters and atom-projected magnetocrystalline anisotropy energies due to Ni doping to understand the experimental observations.

cond-mat.mtrl-sci↗

arXiv2025

A High-Throughput Search for Stable and Magnetically Robust Fe$_3$XY$_2$ Monolayers

We present first principles exploration of 529 Fe$_3$XY$_2$ compounds, where $X$ and $Y$ elements are selected from the $p$-block of the periodic table. Out of the entire set, 31 compounds satisfy all criteria for energetic, dynamic, mechanical, and thermal stability. Our analysis reveals several key trends: halide-containing systems exhibit the highest average magnetic moments and the highest magnetic transition temperatures, highlighting their potential for room-temperature spintronic applications. The majority of stable compounds display perpendicular magnetic anisotropy (PMA), with Fe$_3$SiTe$_2$ exhibiting the strongest PMA among all candidates. Exchange interactions are found to be governed by a dual mechanism, direct exchange between nearest-neighbor Fe atoms and indirect, $p$-orbital-mediated exchange for second-nearest neighbors and beyond. Notably, four compounds have non-centrosymmetric crystal structures and exhibit finite spiralization constants. Among them, Fe$_3$AsBr$_2$ is predicted to host Néel-type skyrmions even at zero external magnetic field, as confirmed by micromagnetic simulations. These findings offer a roadmap for experimental realization of novel 2D ferromagnets with enhanced functionalities.

cond-mat.mtrl-sci↗

arXiv2025

Local structural distortions drive magnetic molecular field in compositionally complex spinel oxide

Understanding how local distortions determine the functional properties of high entropy materials, containing five or more elements at a crystallographic site, is an open challenge. We address this for a compositionally complex spinel oxide (Mn$_{0.2}$Co$_{0.2}$Ni$_{0.2}$Cu$_{0.2}$Zn$_{0.2}$)Cr$_2$O$_4$ ($A^5$Cr$_2$O$_4$). By comparatively examining extended X-ray absorption fine structure on $A^5$Cr$_2$O$_4$ and its parent counterparts $A$Cr$_2$O$_4$ along with density functional theory calculations for multiple configurations, we find that the element-specific distortions go beyond the first neighbor. Specifically, the strong Jahn-Teller distortion present in CuCr$_2$O$_4$ is found to be completely suppressed in $A^5$Cr$_2$O$_4$. Instead, there is a broad distribution of Cu-O and Cu-Cr bond distances while other $A$-O distances acquire certain specific values. This study demonstrates the additional flexibility of a cationic sublattice in maintaining a uniform long-range structure, in contrast to previous reports showing only the accommodative anionic sublattice. Remarkably, despite the presence of multiple magnetic ions and variable bond lengths, the mean field magnetic interactions of $A^5$Cr$_2$O$_4$ exhibit a striking resemblance to those of NiCr$_2$O$_4$. This compelling observation originates from the comparability of bond lengths around Cr in both materials. Our study paves the way for a deeper understanding of the impact of local structural distortions in compositionally complex quantum materials, enabling the targeted design with tailored properties.

cond-mat.mtrl-sci↗

arXiv2025

Complex magnetic exchange, anisotropy and skyrmionic textures in two-dimensional FeXZ$_{2}$ (\textit{X} = Nb, Ta and \textit{Z} = S, Se, Te) ferromagnets

FeNbTe$_{2}$, long known as a van der Waals metallic system, has recently been resynthesized and shown to exhibit ferromagnetic order. In this study, using first-principles density functional theory (DFT), we aim to provide a deeper insight into the magnetic properties of FeNbTe$_{2}$ and its related compounds (FeXZ$_{2}$, \textit{X} = Nb, Ta; \textit{Z} = S, Se, Te), in their two-dimensional form, including their non-centrosymmetric Janus counterparts. Our results indicate that these materials are energetically, dynamically, thermally, and mechanically stable, supporting the possibility of FeNbTe$_{2}$ exfoliation and potential for experimental realization of new compounds. An evolutionary structure search suggests that FeNbTe$_{2}$ retains its monoclinic symmetry in the monolayer form. Our analysis of hopping parameters obtained from Wannierization of DFT bands shows that the nearest-neighbor magnetic interactions are primarily direct, while second-nearest and more distant interactions are mediated by the chalcogen atoms. Interestingly, although the second-nearest-neighbor interactions are smaller in magnitude, they appear to play a key role in determining the magnetic ordering in these systems. We also find evidence of canted magnetic anisotropy in FeXZ$_{2}$ compounds, with relatively strong magnetocrystalline anisotropy energy and easy-axis deviations of up to 41$^\circ$ from the out-of-plane direction-an uncommon and potentially useful feature for spintronic applications. Curie temperatures estimated from Monte Carlo simulations are below room temperature but above cryogenic levels for most compounds. Micromagnetic simulations revealed that Janus-structured FeNbSeTe can host Néel-type skyrmions even in the absence of an external magnetic field, making this compound a suitable candidate for further experimental studies.

cond-mat.mtrl-sci↗

arXiv2025

Emergence of topological superconductivity in the presence of chiral magnetism in 2D CrInTe$_3$

We propose a general framework for designing a two-dimensional (2D) topological superconductor (TSC) using a magnet-superconductor hybrid system. This setup involves a monolayer of CrInTe$_3$, which hosts noncoplanar magnetic textures, in proximity to a 2D $s$-wave superconducting layer. Serving as an alternative to $p$-wave superconductors, this configuration induces a topological superconducting phase and is a promising platform for realizing the 2D Kitaev model, which supports Majorana zero-energy modes through emergent $p$-wave symmetry superconducting pairing. Notably, the magnetic moments break time-reversal symmetry while the superconducting state preserves particle-hole symmetry, placing our system in the Altland-Zirnbauer class $D$ and ensuring robust Majorana excitations. We first perform density functional theory-based simulations to study a monolayer of CrInTe$_3$, from which essential magnetic characteristic parameters, such as Heisenberg exchange interaction and Dzyaloshinskii-Moriya interaction (DMI), are calculated using the state-of-the-art Liechtenstein-Katsnelson-Antropov-Gubanov (LKAG) approach. With a substantial DMI coupling exhibited in CrInTe$_3$, large-scale Monte Carlo simulations reveal the stabilization of a noncoplanar spiral magnetic state as ground state. In this magnetic phase, we observe a transition from corner modes in the zero-energy local density of states (LDOS) to edge modes as the chemical potential ($μ$) varies. Furthermore, under a finite magnetic field, the system enters a mixed magnetic state, characterized by isolated skyrmions and spiral domain walls, which lead to unique low-energy localization of electronic wave functions, rendering the system an insulator. Finally, we discuss potential experimental realizations of TSC in this magnet-superconductor interfacial system, using real-space probes such as scanning tunneling microscopy (STM).

cond-mat.supr-con↗

arXiv2024

Tuning of the ultrafast demagnetization by ultrashort spin polarized currents in multi-sublattice ferrimagnets

Femtosecond laser pulses can be used to induce ultrafast changes of the magnetization in magnetic materials. Several microscopic mechanisms have been proposed to explain the observations, including the transport of ultrashort spin-polarized hot-electrons (SPHE). Such ultrafast spin currents find growing interest because of the recent challenges in ultrafast spintronics however they are only poorly characterized. One of the key challenges is to characterize the spin-polarized ultrafast currents and the microscopic mechanisms behind SPHE induced manipulation of the magnetization, especially in the case of technologically relevant ferrimagnetic alloys. Here, we have used a combined approach using time- and element-resolved X-ray magnetic circular dichroism and theoretical calculations based on atomistic spin-dynamics simulations to address the ultrafast transfer of the angular momentum from spin-polarized currents into ferrimagnetic Fe74Gd26 films and the concomitant reduction of sub-lattice magnetization. Our study shows that using a Co/Pt multilayer as a polarizer in a spin-valve structure, the SPHE drives the demagnetization of the two sub-lattices of the Fe74Gd26 film. This behaviour is explained based on two physical mechanisms, i.e., spin transfer torque and thermal fluctuations induced by the SPHE. We provide a quantitative description of the heat transfer of the ultrashort SPHE pulse to the Fe74Gd26 films, as well as the degree of spin-polarization of the SPHE current density responsible for the observed magnetization dynamics. Our work finally characterizes the spin-polarization of the SPHEs revealing unexpected opposite spin polarization to the Co magnetization, explaining our experimental results.

cond-mat.mtrl-sci↗

arXiv2024

Coexistence of non-trivial van der Waals magnetic orders enable field-free spin-orbit torque switching at room temperature

The discovery of van der Waals (vdW) magnetic materials exhibiting non-trivial and tunable magnetic interactions can give rise to exotic magnetic states, which are not readily attainable with conventional materials. Such vdW magnets can provide a unique platform for studying new magnetic phenomena and realizing magnetization dynamics for energy-efficient and non-volatile spintronic memory and computing technologies. Here, we discover the coexistence of ferromagnetic and antiferromagnetic orders in vdW magnet (Co0.5Fe0.5)5-xGeTe2 (CFGT) CFGT above room temperature, inducing an intrinsic exchange bias and canted perpendicular magnetism. Such non-trivial intrinsic magnetic order enables us to realize energy-efficient, magnetic field-free, and deterministic spin-orbit torque (SOT) switching of CFGT in heterostructure with Pt. The devices show a very large spin Hall conductivity, a low critical current density, and yield a large SOT effective field. These experiments, together with density functional theory and Monte Carlo simulations establish coexisting non-trivial magnetic orders in CFGT that enable field-free SOT magnetization dynamics in spintronic devices.

cond-mat.mes-hall↗

arXiv2023

Strong in-plane magnetic anisotropy (Co0.15Fe0.85)5GeTe2/graphene van der Waals heterostructure spin-valve at room temperature

Van der Waals (vdW) magnets are promising owing to their tunable magnetic properties with doping or alloy composition, where the strength of magnetic interactions, their symmetry, and magnetic anisotropy can be tuned according to the desired application. However, most of the vdW magnet based spintronic devices are so far limited to cryogenic temperatures with magnetic anisotropies favouring out-of-plane or canted orientation of the magnetization. Here, we report room-temperature lateral spin-valve devices with strong in-plane magnetic anisotropy of the vdW ferromagnet (Co0.15Fe0.85)5GeTe2 (CFGT) in heterostructures with graphene. Magnetization measurements reveal above room-temperature ferromagnetism in CFGT with a strong in-plane magnetic anisotropy. Density functional theory calculations show that the magnitude of the anisotropy depends on the Co concentration and is caused by the substitution of Co in the outermost Fe layer. Heterostructures consisting of CFGT nanolayers and graphene were used to experimentally realize basic building blocks for spin valve devices such as efficient spin injection and detection. The spin transport and Hanle spin precession measurements prove a strong in-plane and negative spin polarization at the interface with graphene, which is supported by the calculated spin-polarized density of states of CFGT. The in-plane magnetization of CFGT at room temperature proves its usefulness in graphene lateral spin-valve devices, thus opening further opportunities for spintronic technologies.

cond-mat.mes-hall↗

arXiv2023

Microscopic Insights for Beyond Room-Temperature Ferromagnetism in Ni doped Two-Dimensional Fe$_5$GeTe$_2$

Enhancement of Curie temperature ($T_\mathrm{C}$) of two-dimensional (2D) magnets is immensely desirable for room temperature spintronic applications. Fe$_{5}$GeTe$_{2}$ is an exceptional van der Waals metallic ferromagnet due to its tunable physical properties and relatively higher $T_\mathrm{C}$ than other 2D magnets. Using density functional theory combined with dynamical mean field theory and Monte Carlo simulations, we show that the $T_\mathrm{C}$ of Fe$_{5}$GeTe$_{2}$ monolayer can increase well-above room temperature by substitutional doping with Ni. It is found that two specific sublattices (Fe1 and Fe4) are the first and second most energetically preferred occupation sites for Ni. $T_\mathrm{C}$ of Fe$_{5-δ}$Ni$_δ$GeTe$_{2}$ increases up to $\sim$ 400 K at $δ\sim$20\%. Exchange interactions between particular Fe5-Fe4 pairs play a dominating role in tuning the transition temperature, influenced by doping-induced structural distortions. Finally, we highlight the effect of dynamical electron correlation in site-specific electronic structure and quasi-particle mass of Fe-$d$ orbitals with varying Ni dopi

cond-mat.mtrl-sci↗

arXiv2022

Unraveling effects of electron correlation in two-dimensional Fe$_{n}$GeTe$_{2}$ (n=3, 4, 5) by dynamical mean field theory

The Fe$_{n}$GeTe$_{2}$ systems are newly discovered two-dimensional van-der-Waals materials, exhibiting magnetism at room temperature. The sub-systems belonging to Fe$_{n}$GeTe$_{2}$ class are special because they show site-dependent magnetic behavior. We focus on the critical evaluation of magnetic properties and electron correlation effects in Fe$_{n}$GeTe$_{2}$ ($n$= 3, 4, 5) (FGT) systems performing first-principles calculations. Three different ab-initio approaches have been used, viz., i) standard density functional theory (DFT), ii) incorporating static electron correlation (DFT+U) and iii) inclusion of dynamic electron correlation effect (DFT+DMFT). Our results show that DFT+DMFT is the most accurate technique to correctly reproduce the magnetic interactions and experimentally observed transition temperatures. The inaccurate values of structural parameters, magnetic moments and exchange interactions obtained from DFT+U make this method inapplicable for the FGT family. Correct determination of magnetic properties for this class of materials is important since they are promising candidates for spin transport and spintronic applications at room temperature.

cond-mat.mtrl-sci↗