arXiv subjects

Abhisek Mishra

Publications and source records attributed to Abhisek Mishra.

10 recordsLinked to original sources

arXiv2026

Interface-resolved structural properties of epitaxial Y$_3$Fe$_5$O$_{12}$/ Gd$_3$Fe$_5$O$_{12}$ bilayers grown on GGG(111) by pulsed laser deposition

Epitaxial Y$_3$Fe$_5$O$_{12}$ (YIG) and Gd$_3$Fe$_5$O$_{12}$ (GdIG) thin films, along with their bilayer heterostructures, were grown on Gd$_3$Ga$_5$O$_{12}$(GGG)(111) substrates using pulsed laser deposition. Structural properties were investigated using X-ray diffraction, reciprocal space mapping, and cross-sectional transmission electron microscopy. The results confirm high crystalline quality and coherent epitaxial growth, with RSM revealing a coexistence of strained and partially relaxed regions governed by layer sequence. TEM analysis shows sharp interfaces, columnar microstructures, and antiphase boundaries that facilitate strain relaxation. A comparative study indicates that the GGG/YIG/GdIG stacking sequence exhibits improved structural quality with reduced defect density, attributed to the superior epitaxial growth of YIG on the substrate. These findings highlight the critical role of growth sequence in controlling strain and interfacial structure in garnet heterostructures.

cond-mat.mtrl-sci↗

arXiv2025

Robust Superconductivity and High Upper Critical Fields in Epitaxial cubic W2N Thin Films

Transition Metal Nitrides are a versatile class of materials, combining chemical robustness, high hardness, and superconducting behaviour with critical temperatures between 2 to 10 K. While several binary TMNs have been explored, superconductivity in stoichiometric W2N has remained largely unexplored. Here, we report on superconducting thin films of stoichiometric W2N, demonstrating a distinctly high upper critical field of 8.5 T, uncommon among binary TMNs. This robust superconducting response under high magnetic fields highlights the technological relevance of W2N for integrated quantum and cryogenic electronic platforms. Overall, these results position stoichiometric W2N as a promising addition to the TMN superconducting landscape, opening new avenues for functional materials design based on chemically stable and mechanically resilient nitrides.

cond-mat.supr-con↗

arXiv2025

Enhancement of spin Hall angle by an order of magnitude via Cu intercalation in MoS$_2$/CoFeB heterostructures

Transition metal dichalcogenides (TMDs) are a novel class of quantum materials with significant potential in spintronics, optoelectronics, valleytronics, and opto-valleytronics. TMDs exhibit strong spin-orbit coupling, enabling efficient spin-charge interconversion, which makes them ideal candidates for spin-orbit torque-driven spintronic devices. In this study, we investigated the spin-to-charge conversion through ferromagnetic resonance in MoS$_2$/Cu/CoFeB heterostructures with varying Cu spacer thicknesses. The conversion efficiency, quantified by the spin Hall angle, was enhanced by an order of magnitude due to Cu intercalation. Magneto-optic Kerr effect microscopy confirmed that Cu did not significantly modify the magnetic domains, indicating its effectiveness in decoupling MoS$_2$ from CoFeB. This decoupling preserves the spin-orbit coupling (SOC) of MoS$_2$ by mitigating the exchange interaction with CoFeB, as proximity to localized magnetization can alter the electronic structure and SOC. First-principles calculations revealed that Cu intercalation notably enhances the spin Berry curvature and spin Hall conductivity, contributing to the increased spin Hall angle. This study demonstrates that interface engineering of ferromagnet/TMD-based heterostructures can achieve higher spin-to-charge conversion efficiencies, paving the way for advancements in spintronic applications.

cond-mat.mtrl-sci↗

arXiv2025

Lattice Mismatch Driven In Plane Strain Engineering for Enhanced Upper Critical Fields in Mo2N Superconducting Thin Films

Transition metal nitrides are a fascinating class of hard coating material that provide an excellent platform for investigating superconductivity and fundamental electron phonon interactions. In this work the structural morphological and superconducting properties have been studied for Mo2N thin films deposited via direct current magnetron sputtering on cplane Al2O3 and MgO substrates to elucidate the effect of internal strain on superconducting properties. High resolution X Ray diffraction and time of flight elastic recoil detection analysis confirms the growth of single phase Mo2N thin films exhibiting epitaxial growth with twin domain structure. Low temperature electrical transport measurements reveal superconducting transitions at 5.2 K and 5.6 K with corresponding upper critical fields of 5 T and 7 T for the films deposited on Al2O3 and MgO, respectively. These results indicate strong type II superconductivity and the observed differences in superconducting properties are attributed to substrate induced strain which leads to higher e ph coupling for the film on MgO substrate. These findings highlight the tunability of superconducting properties in Mo2N films through strategic substrate selection.

cond-mat.supr-con↗

arXiv2024

Efficient spin to charge conversion and spin memory loss mitigation in oriented $\text{RuO}_2$ films

$\text{RuO}_2$, a transition metal oxide, is attracting attention in spintronics for its unique altermagnetic properties, which influence spin currents. Its ability to produce large spin-orbit torques and spin Hall effects is key for energy-efficient magnetic memory and logic devices. Additionally, the tunable thickness and crystallinity of $\text{RuO}_2$ thin films optimize torque efficiency for low-power switching. Spin pumping, a versatile method for investigating spin dynamics in $\text{RuO}_2$ thin films, has garnered considerable interest because of its straightforward, non-invasive and uncomplicated approach to addressing impedance mismatch and direct measurement of spintronic parameters. Here we present a systematic and detailed analysis on the efficient spin to charge conversion in (110)-oriented $\text{RuO}_2$ films with amorphous CoFeB as spin source. The spin Hall angle, and spin diffusion length were estimated to be 0.14 $\pm$ 0.01 and 4.58 $\pm$ 0.40 nm, respectively. The spin Hall conductivity of 998.89 $\pm$ 58.23 $\hbar \cdot \frac{Ω^{-1} \, \text{cm}^{-1}}{e}$ has been estimated which is theoretically predicted to be of the similar order. The interfacial spin transparency has been achieved to be 90%. We have shown that the spin memory loss at the $\text{RuO}_2$/CoFeB interface is 15%, which is very small.

cond-mat.mtrl-sci↗

arXiv2024

Magnon mediated spin pumping by coupled ferrimagnetic garnets heterostructure

Spin pumping has significant implications for spintronics, providing a mechanism to manipulate and transport spins for information processing. Understanding and harnessing spin currents through spin pumping is critical for the development of efficient spintronic devices. The use of a magnetic insulator with low damping, enhances the signal-to-noise ratio in crucial experiments such as spin-torque ferromagnetic resonance (FMR) and spin pumping. A magnetic insulator coupled with a heavy metal or quantum material offers a more straight forward model system, especially when investigating spin-charge interconversion processes to greater accuracy. This simplicity arises from the absence of unwanted effects caused by conduction electrons unlike in ferromagnetic metals. Here, we investigate the spin pumping in coupled ferrimagnetic (FiM) Y3Fe5O12 (YIG)/Tm3Fe5O12 (TmIG) bilayers combined with heavy-metal (Pt) using the inverse spin Hall effect (ISHE). It is observed that magnon transmission occurs at both of the FiMs FMR positions. The enhancement of spin pumping voltage (Vsp) in the FiM garnet heterostructures is attributed to the strong interfacial exchange coupling between FiMs. The modulation of Vsp is achieved by tuning the bilayer structure. Further, the spin mixing conductance for these coupled systems is found to be 10^18 m^-2. Our findings describe a novel coupled FiM system for the investigation of magnon coupling providing new prospects for magnonic devices.

cond-mat.mtrl-sci↗

arXiv2023

Structural deformation and irreversible magnetic properties of flexible Co/Pt and Co/Pd thin films

The successful commercialization of flexible spintronic devices requires a complete understanding of the impact of external strain on the structural, electronic, and magnetic properties of a system. The impact of bending-induced strain on flexible films is studied quite well. However, little is known about the effect of other modes of flexibility, e.g., wrinkling, twisting, peeling, and stretching on the functional properties of flexible films. In this context, perpendicular magnetic anisotropic Co/Pt and Co/Pd thin films are prepared on flexible Kapton substrates, and the impact of the peeling mode is studied in detail. The peeling method generates numerous cracks, and buckling in the thin film, along with localized blister formation imaged by scanning electron microscopy. Further, the resistivity measurement confirms a significant enhancement in sample resistance owing to the severe damage of the films. The structural discontinuities strongly affect the magnetization reversal phenomena as measured by the magneto-optic Kerr effect (MOKE)-based microscopy. The bubble domains got converted to elongated-shaped domains due to several hindrances to the wall motion after strain application. Further, the relaxation measurements reveal that the thermal energy is insufficient to switch the magnetization at a few areas due to their high pinning potential associated with the damages. In contrast to bending-induced strain, here, all the modifications in the functional properties are found to be irreversible in nature.

cond-mat.mtrl-sci↗

arXiv2023

Self-induced inverse spin Hall effect in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ films

The efficient generation of spin currents and spin torques via spin-orbit coupling is an important goal of spintronics research. One crucial metric for spin current generation is the spin Hall angle, which is the ratio of the spin Hall current to the transversely flowing charge current. A typical approach to measure the spin Hall angle in nonmagnetic materials is to generate spin currents via spin pumping in an adjacent ferromagnetic layer and measure the transverse voltage from the inverse spin Hall effect in the nonmagnetic layer. However, given that the spin Hall effect also occurs in ferromagnets, single ferromagnetic layers could generate a self-induced transverse voltage during spin pumping as well. Here we show that manganite based La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO) films deposited by pulsed laser deposition exhibit a significant self-induced inverse spin Hall voltage while undergoing spin pumping. We observe efficient spin to charge conversion in the LSMO films via the inverse spin Hall effect. A spin pumping voltage of 1.86 $μ$V is observed in the LSMO (12 nm) film. Using density functional theory and the Kubo formalism, we calculate the intrinsic spin current conductivities of these films and show that they are in reasonable agreement with the experimental measurements.

physics.app-ph↗

arXiv2021

Enhancement of in-plane anisotropy in MoS2/CoFeB bilayers

Transition metal dichalcogenides (TMD) possess novel properties which makes them potential candidates for various spintronic applications. Heterostructures of TMD with magnetic thin film have been extensively considered for spin-orbital torque, enhancement of perpendicular magnetic anisotropy etc. However, the effect of TMD on magnetic anisotropy in heterostructures of in-plane magnetization has not been studied so far. Further the effect of the TMD on the domain structure and magnetization reversal of the ferromagnetic system is another important aspect to be understood. In this context we study the effect of MoS2, a well-studied TMD material, on magnetic properties of CoFeB in MoS2/CoFeB heterostructures. The reference CoFeB film possess a weak in-plane anisotropy. However, when the CoFeB is deposited on MoS2 the in-plane anisotropy is enhanced as observed from magneto optic Kerr effect (MOKE) microscopy as well as ferromagnetic resonance (FMR). Magnetic domain structure and magnetization reversal have also been significantly modified for the MoS2/CoFeB bilayer as compared to the reference CoFeB layer. Frequency and angle dependent FMR measurement show that the magnetic anisotropy of CoFeB increases with increase in thickness of MoS2 in the MoS2/CoFeB heterostructures.

cond-mat.mtrl-sci↗

arXiv2021

Spin pumping and inverse spin Hall effect in CoFeB/IrMn heterostructures

High spin to charge conversion efficiency is the requirement for the spintronics devices which is governed by spin pumping and inverse spin Hall effect (ISHE). In last one decade, ISHE and spin pumping are heavily investigated in ferromagnet/ heavy metal (HM) heterostructures. Recently antiferromagnetic (AFM) materials are found to be good replacement of HMs because AFMs exhibit terahertz spin dynamics, high spin-orbit coupling, and absence of stray field. In this context we have performed the ISHE in CoFeB/ IrMn heterostructures. Spin pumping study is carried out for $Co_{40}Fe_{40}B_{20} (12\ nm)/ Cu (3\ nm)/ Ir_{50}Mn_{50} (t\ nm)/ AlO_{x} (3\ nm)$ samples where \textit{t} value varies from 0 to 10 nm. Damping of all the samples are higher than the single layer CoFeB which indicates that spin pumping due to IrMn is the underneath mechanism. Further the spin pumping in the samples are confirmed by angle dependent ISHE measurements. We have also disentangled other spin rectifications effects and found that the spin pumping is dominant in all the samples. From the ISHE analysis the real part of spin mixing conductance (\textit{$g_{r}^{\uparrow \downarrow}$}) is found to be 0.704 $\pm$ 0.003 $\times$ $10^{18}$ $m^{-2}$.

cond-mat.mes-hall↗