arXiv subjects

Soumyarup Hait

Publications and source records attributed to Soumyarup Hait.

5 recordsLinked to original sources

arXiv2026

Temperature-Dependent Spin-Orbit Torque Generation in Perpendicularly Magnetized Topological Insulator-Magnetic Multilayer Heterostructures

We report a comprehensive temperature-dependent investigation of spin-orbit torque (SOT) generation in heterostructures comprising a perpendicularly magnetized metallic multilayer grown on top of a topological insulator (TI) epilayer. Temperature-dependent second-harmonic Hall measurements reveal distinct trends in the magnitude of the spin-orbit torque across the studied heterostructures. Samples incorporating Bi2Se3 exhibit torques reaching approximately 12 mT/(10^12 A m^-2) at 15 K, around 5 times larger than those in a multilayer without the topological layer. The structure with a thin 2-nm Ta buffer for the multilayer shows the strongest enhancement and a pronounced increase at low temperatures, highlighting efficient spin-current generation from the topological surface states. In contrast, the sample with a 10 nm-thick Ta spacer exhibits reduced torque efficiency, consistent with partial attenuation of spin transmission through the buffer. Systems lacking Bi2Se3 but containing two heavy metals (Ta and Pt) yield significantly smaller torques, around 2.5 mT/(10^12 A m^-2), despite the presence of conventional spin Hall sources. These observations underscore the dominant role of TI-derived spin-momentum-locked currents in driving large damping-like torques and their sensitivity to interfacial structure and buffer-layer thickness.

cond-mat.mes-hall↗

arXiv2026

Tailoring Ultrathin Magnetic Multilayers at Terraced Topologically Insulating Interfaces for Perpendicularly Magnetized Domains

Topological insulators and skyrmion-hosting, chiral magnetic multilayers are two well-explored areas of modern condensed matter physics, each offering unique advantages for spintronics applications. In this paper, we demonstrate the optimization process for the growth of a Bi$_2$Se$_3$/buffer/[Pt/CoB/Ru]$_{\times N}$ heterostructure that combines these two material classes: the Bi$_2$Se$_3$ epilayer was grown by molecular beam epitaxy before transfer under ultrahigh vacuum to a separate growth chamber where the polycrystalline metallic multilayer was sputter deposited. The structure of the samples was characterized by co-fitted X-ray and polarized neutron reflectometry measurements and scanning transmission electron microscopy. Polarized neutron models and standard magnetometry show that a buffer layer exceeding a critical thickness is required to obtain the desired uniform, perpendicular magnetic anisotropy in every magnetic layer in the multilayer. Samples with both Ta and Mo buffers were used requiring thicknesses of 1.5 and 0.9 nm respectively. In minimizing the Bi$_2$Se$_3$ terracing, buffered samples yield well-defined, out-of-plane, magnetic domains suitable for spin-orbit torque induced manipulation as determined by X-ray photoemission electron microscopy.

cond-mat.mtrl-sci↗

arXiv2025

Temperature gradient-driven motion of magnetic domains in a magnetic metal multilayer by entropic forces

We studied the displacement of magnetic domains under temperature gradients in perpendicularly magnetized Ta/[Pt/Co$_{68}$B$_{32}$/Ir]$_{\times 10}$/Pt multilayer tracks with microfabricated Pt heaters/thermometers by magnetic force microscopy (MFM). Subtracting out the effects of the Oersted field from the heating current reveals the pure temperature gradient-driven motion, which is always towards the heater. The higher the thermal gradient along the track (owing to proximity to the heater or larger heater currents), the greater the observed displacements of the domains, up to a velocity of around 1~nm/s in a temperature gradient of 20~K/$μ$m. Quantitative estimates of the strength of different driving mechanisms show that entropic forces dominate over those arising from the spin Seebeck and spin-dependent Seebeck effects.

cond-mat.mes-hall↗

arXiv2024

Large Orbital to Charge Conversion in Weak Spin Orbit Coupling Element Zr via Spin Orbital Pumping and Spin Orbital Seebeck Effect

The generation of spin-orbital currents is crucial for advancing energy-efficient spintronic devices. Here, the intricate process involved in the generation and conversion of spin and orbital to charge currents in Zr(t=2, 3, 4.5, 6, &10nm)/Co60Fe20B20(CFB), Zr/Pt/CFB, and Zr/Pt/CFB/Pt heterostructures are investigated using spin-orbital pumping ferromagnetic resonance and longitudinal spin-orbital Seebeck effect measurements. The moderate spin-orbit coupling (SOC) in the CFB layer facilitates the simultaneous generation of spin and orbital currents, which are transferred into adjacent Zr and Pt layers. Different spin-orbital to charge current contributions, namely, Inverse spin Hall effect (ISHE), Inverse orbital Hall effect (IOHE), and Inverse orbital Rashba-Edelstein effect (IOREE) are analyzed. Notably, introducing a single Pt layer increases the spin-orbital to charge current conversion via combined effects: ISHE in Pt, IOREE in Zr/Pt interface. An enhanced effective spin-orbital Hall angle (θ_eff) of 0.120 {\pm} 0.004 is observed for Zr/Pt/CFB, compared to that of 0.065 {\pm} 0.002 for the Zr/CFB, and 0.077 {\pm} 0.003 for the Zr/Pt/CFB/Pt heterostructures. These findings provide new insights into orbital-moment dependent phenomena and offer promising avenues for developing advanced spintronic devices exploiting both spin and orbital degrees of freedom, even in materials with lower SOC.

physics.app-ph↗

arXiv2019

Spin pumping and spin torque in interfacial tailored Co2FeAl/\b{eta}-Ta layers

The Heusler ferromagnetic (FM) compound Co2FeAl interfaced with a high-spin orbit coupling non-magnetic (NM) layer is a promising candidate for energy efficient spin logic circuits. The circuit potential depends on the strength of angular momentum transfer across the FM/NM interface; hence, requiring low spin memory loss and high spin-mixing conductance. To highlight this issue, spin pumping and spin-transfer torque ferromagnetic resonance measurements have been performed on Co_2FeAl/β-Ta heterostructures tailored with Cu interfacial layers. The interface tailored structure yields an enhancement of the effective spin-mixing conductance. The interface transparency and spin memory loss corrected values of the spin-mixing conductance, spin Hall angle and spin diffusion length are found to be 3.40 \pm 0.01 \times 10^{19} m^{-2}, 0.029 \pm 0.003, and 2.3 \pm 0.5 nm, respectively. Furthermore, a high current modulation of the effective damping of around 2.1 % has been achieved at an applied current density of 1 \times 10^9 A/m^2 , which clearly indicates the potential of using this heterostructure for energy efficient control in spin devices

cond-mat.mtrl-sci↗