arXiv subjects

Muhammad Aziz Majidi

Publications and source records attributed to Muhammad Aziz Majidi.

18 recordsLinked to original sources

arXiv2026

Spin Response Properties in Electronically Robust Ferromagnetic Strained CrSiSe$_3$ Monolayer under External Electric Fields

Integrating two-dimensional van der Waals magnets into field-effect spintronic devices requires robust charge stability and tunable spin responses. In this study, we investigate the electronic, topological, magnonic, and magneto-optical properties of the strain-engineered ferromagnetic CrSiSe$_3$ monolayer under out-of-plane external electric fields by using first-principles calculations. We find that for this material, the intrinsic charge sector, including the indirect band gap, charge Berry curvature, optical conductivities, and magneto-optical Kerr effect spectra, exhibits exceptional robustness against applied fields up to 0.3 V/$\r{A}$. Conversely, the spin degrees of freedom demonstrate highly sensitive tunability. Electrostatic gating significantly modulates the spin Berry-like curvature, driving a non-monotonic enhancement in the spin Hall conductivity. Furthermore, external fields effectively tune collective magnon excitations by modifying microscopic Heisenberg exchange interactions. Such coexistence of robust charge immunity and flexible spin manipulation establishes the strained CrSiSe$_3$ monolayer as a promising platform for stable spintronic devices.

cond-mat.mtrl-sci↗

arXiv2026

Geometry-controlled magnon-polaritons of double magnetic films in planar cavities

Planar cavity magnonics has been developed mainly for a single magnetic film, leaving multilayer behavior in spatially resolved cavity scattering largely unexplored. Here, we introduce a double layer planar cavity with two magnetic films embedded in the same microwave cavity to derive a full two-film scattering theory in the macrospin ($J = 0$) limit and recover the exact zero-gap half-thickness limit, thereby benchmarking the model against the known one-film result. We find that the double layer model actively enables geometry-controlled bright-channel enhancement, demonstrating that the magnon-photon coupling depends on spatial placement rather than just total magnetic volume. Antinode-compatible placements increase the coupling, while node-compatible placements suppress it. Weak symmetry breaking also transfers finite cavity weight to a mode dark in the symmetric limit, producing an additional branch without destroying the main avoided crossing. Finally, a reduced multimode theory for $J\neq 0$ predicts family-resolved bright and dark channels for odd standing-spin-wave modes.

cond-mat.mes-hall↗

arXiv2025

Spin current generation driven by skyrmion dynamics under magnetic anisotropy and polarized microwaves

We have investigated the spin-current pumped by the skyrmion-host material with the lack of inversion symmetry through the microwave resonance process. The effects of magnetic anisotropy and polarized microwaves are examined by micromagnetic simulations. Our results reveal two distinct skyrmion phases, designated as SkX type-I and II, which emerge at low ($K_z<0.1$ meV) and high ($K_z>0.1$ meV) magnetic anisotropy constants, respectively, having different characteristics of spin excitations. The SkX type-I exhibits spin dynamics where the resonant frequency of the breathing mode is lying in between the clockwise and counterclockwise gyration modes of Bloch-type skyrmion at a very low anisotropy, and is crossing over the counterclockwise mode at $K_z \sim 0.04$ meV. Meanwhile, the SkX type-II exhibits distinct spin excitations in which the clockwise mode is notably absent, while the counterclockwise modes exist at both low and high resonant frequencies. This suggests that the magnetic anisotropy plays an essential role in the spin dynamics. Furthermore, the resulting spin excitations induce spin currents with exotic features under the polarized microwaves. The spin currents induced, for instance, by low-lying in-plane excitations are strongly enhanced under the left-handed circularly polarized microwaves, but quenched by the right-handed circularly polarized microwaves regardless of the sign of the Dzyaloshinskii-Moriya interaction. These results may pave the way for understanding the non-trivial interplay between magnetic anisotropy and polarized microwaves in the generation of spin currents by a resonant process.

cond-mat.mtrl-sci↗

arXiv2024

Impact of Monoatomic Vacancies in 2D Materials on the Performance of Magnetic Tunnel Junction Devices: Insights from Configurations and Interface Interactions

We investigate the impact of monoatomic vacancies in 2D materials on the performance of magnetic tunnel junction (MTJ) devices using first-principles calculations within Density Functional Theory (DFT). Specifically, we analyze the influence on hexagonal boron nitride (hBN) with various layer configurations, uncovering distinct transmission probability patterns. Transmission calculations were conducted using the Landauer-B\"uttiker formula employing the Non-Equilibrium Green's Function (NEGF) method. In the Ni/hBN(V$_B$)-hBN/Ni system, a significant reduction in transmission probability was observed compared to non-vacancy configurations. However, when two hBN vacancies were considered, creating the Ni/hBN(V$_B$)-hBN(V$_B$)/Ni MTJ system, a new transmission channel mediated by vacancy localized states emerged. The introduction of a monoatomic boron vacancy in the middle hBN layer of the Ni/3hBN/Ni system revealed nuanced effects on the transmission probability, highlighting alterations in the spin minority and majority channels. Additionally, we explore the monoatomic vacancy in the graphene layer in the Ni/hBN-Gr-hBN/Ni MTJ, uncovering a unique transmission channel influenced by the proximity effect. Our findings suggest that the creation of monoatomic vacancies on the insulator barrier of 2D materials induces distinctive characteristics shaped by the interaction between the surface state of the electrode and the localized state of the monoatomic vacancy layer in the MTJ system.

cond-mat.mtrl-sci↗

arXiv2024

Ti substitution on Fe sites significantly changes the electronic properties of orthorhombic LaFeO3 perovskites (A first-principles study)

A large number of published experimental works suggest that when the Fe ions in orthorhombic LaFeO3 are substituted, band gap reduction is expected. However, recent experimental works observe band gap enhancement with increasing Ti ions replacing Fe ions. While satisfactory explanation on such observations seem absent, a first principles investigation may answer what should really happen. We investigate from first-principles the influence of Ti substitution on LaFeO3 at Fe-site as a function of substitution concentration. Amongst the five investigated models, we found that as the Ti substitution concentration increases, the electronic band gap at Fermi level decreases. However, in the model where two Ti ions replace Fe sites in an anti-symmetric arrangement, the Fermi level is crossed. We found that band gap reductions could be caused by the decreased in field splitting between the Fe 3d orbitals and charge competition between Fe-O and Ti-O bonds as inferred from density of states analysis. While band gap reduction with increasing substitution implies better conductivity, cohesive energy becomes less negative although the perovskite distortion parameter does not differ significantly between each models.

cond-mat.mtrl-sci↗

arXiv2023

High Magnetoresistance Ratio on hBN Boron-Vacancy/Graphene Magnetic Tunnel Junction

We presents a new strategy to create a van der Waals-based magnetic tunnel junction (MTJ) that consists of a three-atom layer thickness of graphene (Gr) sandwiched with hexagonal boron nitride (hBN) by introducing a monoatomic Boron vacancy in both hBN layers. The magnetic properties and electronic structure of the system were investigated using density functional theory (DFT), while the transmission probability of the MTJ was investigated using the Landauer-B\"uttiker formalism within the non-equilibrium Green function method. The Stoner gap was found to be created between the spin-majority channel and the spin-minority channel on LDOS of the hBN monoatomic boron-vacancy (V$_B$) near the vicinity of Fermi energy, creating a possible control of the spin valve by considering two different magnetic allignment of hBN(V$_B$) layers, anti-parallel and parallel configuration. The results of the transmission probability calculation showed a high electron transmission in the parallel configuration of the hBN(V$_B$) layers and a low transmission when the antiparallel configuration was considered. A high TMR ratio of approximately 400% was observed when comparing the antiparallel and parallel configuration of hBN(V$_B$) layers in the hBN (V$_B$)/Gr/hBN(V$_B$), giving the highest TMR for the thinnest MTJ system.

cond-mat.mes-hall↗

arXiv2023

High-performance Kerr quantum battery

We propose and investigate the performance of a hybrid quantum battery, the so-called Kerr quantum battery, which consists of two interacting quantum oscillators, i.e., the charger is a harmonic oscillator and the battery is an anharmonic oscillator involving the Kerr nonlinearity. Such a setup creates nonuniform spacing between energy levels of the quantum oscillator that increases with the energy level. We find that the Kerr quantum battery can store more energy than the qubit battery and reaches maximum stored energy faster than the harmonic oscillator battery. In particular, the average charging power of the Kerr quantum battery is larger than the qubit battery. Furthermore, most of the stored energy in the Kerr quantum battery can be extracted for work. All of the properties of the Kerr quantum battery are controlled by the strength of nonlinearity, in which the enhancement of the nonlinearity transforms the battery from a harmonic oscillator to a qubit.

quant-ph↗

arXiv2023

Electrically controllable exchange bias via interface magnetoelectric effect

Exchange bias is a unidirectional magnetic anisotropy that often arise from interfacial interaction of a ferromagnetic and antiferromagnetic layers. In this article, we show that a metallic layer with spin-orbit coupling can induces an exchange bias via an interface magnetoelectric effect. In linear response regime, the interface magnetoelectric effect is induced by spin-orbit couplings that arises from the broken symmetry of the system. Furthermore, we demonstrate that the exchange bias can be controlled by electric field.

cond-mat.mes-hall↗

arXiv2023

Computational study of III-V direct-gap semiconductors for thermoradiative cell applications

We investigate the performance of thermoradiative (TR) cells using the III-V group of semiconductors, which include GaAs, GaSb, InAs, and InP, with the aim of determining their efficiency and finding the best TR cell materials among the III-V group. The TR cells generate electricity from thermal radiation, and their efficiency is influenced by several factors such as the bandgap, temperature difference, and absorption spectrum. To create a realistic model, we incorporate sub-bandgap and heat losses in our calculations and utilize density-functional theory to determine the energy gap and optical properties of each material. Our findings suggest that the effect of absorptivity on the material, especially when the sub-bandgap and heat losses are considered, can decrease the efficiency of TR cells. However, careful treatment of the absorptivity indicates that not all materials have the same trend of decrease in the TR cell efficiency when taking the loss mechanisms into account. We observe that GaSb exhibits the highest power density, while InP demonstrates the lowest one. Moreover, GaAs and InP exhibit relatively high efficiency without the sub-bandgap and heat losses, whereas InAs display lower efficiency without considering the losses, yet exhibit higher resistance to sub-bandgap and heat losses compared to the other materials, thus effectively becoming the best TR cell material in the III-V group of semiconductors.

cond-mat.mes-hall↗

arXiv2022

Enhancement of spin mixing conductance by $s$-$d$ orbital hybridization in heavy metals

In a magnetic multilayer, the spin transfer between localized magnetization dynamics and itinerant conduction spin arises from the interaction between a normal metal and an adjacent ferromagnetic layer. The spin-mixing conductance then governs the spin-transfer torques and spin pumping at the magnetic interface. Theoretical description of spin-mixing conductance at the magnetic interface often employs a single conduction-band model. However, there is orbital hybridization between conduction $s$ electron and localized $d$ electron of the heavy transition metal, in which the single conduction-band model is insufficient to describe the $s$-$d$ orbital hybridization. In this work, using the generalized Anderson model, we estimate the spin-mixing conductance that arises from the $s$-$d$ orbital hybridization. We find that the orbital hybridization increases the magnitude of the spin-mixing conductance.

cond-mat.mes-hall↗

arXiv2022

Effect of interfacial spin mixing conductance on gyromagnetic ratio of Gd substituted Y$_{3}$Fe$_{5}$O$_{12}$

Due to its low intrinsic damping, Y$_3$Fe$_5$O$_{12}$ and its substituted variations are often used for ferromagnetic layer at spin pumping experiment. Spin pumping is an interfacial spin current generation in the interface of ferromagnet and non-magnetic metal, governed by spin mixing conductance parameter $G^{\uparrow\downarrow}$. $G^{\uparrow\downarrow}$ has been shown to enhance the damping of the ferromagnetic layer. The theory suggested that the effect of $G^{\uparrow\downarrow}$ on gyromagnetic ratio only come from its negligible imaginary part. In this article, we show that the different damping of ferrimagnetic lattices induced by $G^{\uparrow\downarrow}$ can affect the gyromagnetic ratio of Gd-substituted Y$_3$Fe$_5$O$_{12}$.

cond-mat.mes-hall↗

arXiv2021

Ultimate In-plane Magnetoresistance Ratio of Graphene by Controlling the Gapped Dirac Cone through Pseudospin

$\require{mediawiki-texvc}$ A theoretical study is presented on the in-plane conductance of graphene that is partially sandwiched by Ni(111) slabs with a finite size and atom-scale width of $\approx12.08 \AA$. In the sandwiched part, the gapped Dirac cone of graphene can be controlled via pseudospin by changing the magnetic alignment of the Ni(111) slabs. When the magnetic moments of the upper and lower Ni(111) slabs have antiparallel and parallel configurations, the bandgap at the Dirac cone is open and closed, respectively. The transmission probability calculation for the in-plane conductance of the system indicated that the antiparallel configuration would result in nearly zero conductance of $E-E_F=0.2$ eV. In the parallel configuration, the transmission probability calculation indicated that the system would have a profile similar to that of pristine graphene. A comparison of the transmission probabilities of the antiparallel and parallel configurations indicated that a high magnetoresistance of $1450\%$ could be achieved. An ultimate magnetoresistance can be expected if the Ni(111) slab widths are increased to the nanometer scale.

cond-mat.mes-hall↗

arXiv2021

High magnetoresistance of hexagonal boron nitride-graphene heterostructure-based MTJ through excited-electron transmission

This work presents an ab-initio study of a few-layers hexagonal boron nitride (hBN) and hBN-graphene heterostructure sandwiched between Ni(111) layers. The aim of this study is to understand the electron transmission process through the interface. Spin-polarized density functional theory calculations and transmission probability calculations were conducted on Ni(111)/$n$hBN/Ni(111) with $n$ = 2, 3, 4, and 5 as well as on Ni(111)/hBN-Gr-hBN/Ni(111). Slabs with magnetic alignment in an anti-parallel configuration (APC) and parallel configuration (PC) were considered. The pd-hybridizations at both the upper and lower interfaces between the Ni slabs and hBN were found to stabilize the system. The Ni/nhBN/Ni magnetic tunnel junction (MTJ) was found to exhibit a high tunneling magnetoresistance (TMR) ratio at ~0.28 eV for $n$ = 2 and 0.34 eV for $n$ > 2, which are slightly higher than the Fermi energy. The observed shifting of this high TMR ratio originates from the transmission of electrons through the surface states of the $d_{z^2}$-orbital of Ni atoms at interfaces which are hybridized with the $p_z$-orbital of N atoms. In the case of $n$ > 2, the proximity effect causes an evanescent wave, contributing to decreasing transmission probability but increasing the TMR ratio. However, TMR ratio, as well as transmission probability, was found to be increased, by replacing the unhybridized hBN layer of the Ni/3hBN/Ni MTJ with graphene, thus becoming Ni/hBN-Gr-hBN/Ni. A TMR ratio as high as ~1200% was observed at an energy of 0.34 eV, which is higher than the Fermi energy. Furthermore, a design is proposed for a device based on a new reading mechanism using the high TMR observed just above the Fermi energy level.

cond-mat.mtrl-sci↗

arXiv2021

Yukawa potential for realistic prediction of Hubbard and Hund interaction parameters for transition metals

The generalized Hubbard model is an important theoretical model for modeling strongly correlated materials. To be able to theoretically predict the properties of the materials, the model requires Hubbard's $U$ and Hund's $J$ parameter that represent the on-site Coulomb and exchange interaction, respectively. For bare Coulomb interactions, the analytic expression of $U$ and $J$ are analytically described by Racah's $A,B,C$ parameters. However, the values of $U$ are too large for transition-metal-based materials. To obtain more accurate values for realistic materials, we employ a Yukawa-type screened Coulomb interaction, characterized by screening constant $λ$. We characterize $λ$ for transition metals. The modified $A,B,C$ parameters give a more realistic $U$ and $J$ values.

cond-mat.str-el↗

arXiv2021

Effects of screened Coulomb interaction on spin transfer torque

In a magnetic multilayer, magnetizations can be manipulated by spin transfer torque. Both spin transfer torque and its reciprocal effect, spin pumping, are governed by spin mixing conductance. The magnitude of spin mixing conductance at the interface of nearly magnetic metal has been theoretically shown to be enhanced by electron-electron interaction. However, experiments show both increasing and decreasing values of spin mixing conductance for metals with larger electron-electron interaction. Here we take into account the effect of electron-electron interaction on the screening of the Coulomb interaction at the magnetic interface to correctly describe the experiment.

cond-mat.mes-hall↗

arXiv2019

Spin-Current Control by Induced Electric-Polarization Reversal in Ni/hBN/Ni: A Cross-Correlation Material

We undertook an ab-initio study of hexagonal boron nitride (hBN) sandwiched between Ni(111) layers to examine the interface of this material structure. We considered Ni(111)/hBN/Ni(111) with a slab with three Ni atomic layers to determine the exact atom arrangement at the interface. The density functional theory calculations for 36 stacking arrangements, which are doubled with respect to the magnetic alignment of slabs in an anti-parallel configuration (APC) and parallel configuration (PC), revealed that the number of formed weak chemical bonds, in the pd-hybridization between the N and Ni atoms, is decisive. A maximum of two pd-hybridization bonds stabilized the structure, with APC proving to be the most favorable magnetic alignment, in line with the results of previous experimental studies. In the lowest energy state, an induced magnetic moment at an N site appears when N is moved closer to one of the Ni atoms. Interestingly, the moment direction is switched by the position of the N layer in the resulting bi-stable state with electrical polarization when APC is chosen. The transmission probability calculation of Ni/hBN/Ni having the determined interface structure at the center of the junction exhibits a spin-filtering effect where the spin-polarized current is controlled by the electric field when a field-induced reversal of the polarization is realized.

cond-mat.mes-hall↗

arXiv2015

Theoretical study of optical conductivity of graphene with magnetic and nonmagnetic adatoms

We present a theoretical study of the optical conductivity of graphene with magnetic and nonmagnetic adatoms. First, by introducing alternating potential in a pure graphene, we demonstrate a gap formation in the density of states and the corresponding optical conductivity. We highlight the distinction between such a gap formation and the so-called Pauli blocking effect. Next, we apply this idea to graphene with adatoms by introducing magnetic interactions between the carrier spins and the spins of the adatoms. Exploring various possible ground-state spin configurations of the adatoms, we find that antiferromagnetic configuration yields the lowest total electronic energy, and is the only configuration that forms a gap. Furthermore, we analyze four different circumstances leading to similar gaplike structures and propose a means to interpret the magneticity and the possible orderings of the adatoms on graphene solely from the optical conductivity data. We apply this analysis to the recently reported experimental data of oxygenated graphene.

cond-mat.str-el↗

arXiv2011

Theory of high energy optical conductivity and the role of oxygens in manganites

Recent experimental study reveals the optical conductivity of La$_{1-x}$Ca$_x$MnO$_3$ over a wide range of energy and the occurrence of spectral weight transfer as the system transforms from paramagnetic insulating to ferromagnetic metallic phase [Rusydi {\it et al.}, Phys. Rev. B {\bf 78}, 125110 (2008)]. We propose a model and calculation within the Dynamical Mean Field Theory to explain this phenomenon. We find the role of oxygens in mediating the hopping of electrons between manganeses as the key that determines the structures of the optical conductivity. In addition, by parametrizing the hopping integrals through magnetization, our result suggests a possible scenario that explains the occurrence of spectral weight transfer, in which the ferromagnatic ordering increases the rate of electron transfer from O$_{2p}$ orbitals to upper Mn$_{e_g}$ orbitals while simultaneously decreasing the rate of electron transfer from O$_{2p}$ orbitals to lower Mn$_{e_g}$orbitals, as temperature is varied across the ferromagnetic transition. With this scenario, our optical conductivity calculation shows very good quantitative agreement with the experimental data.

cond-mat.mtrl-sci↗