Thermal gradient-driven skyrmion dynamics with near-zero skyrmion Hall angle

TL;DR

This study investigates thermal-gradient-driven dynamics of Neel skyrmions in a Co/Pt bilayer racetrack using micromagnetic simulations. Skyrmions move predominantly toward the hotter region with an almost vanishing skyrmion Hall angle, and the longitudinal velocity scales with the thermal gradient $\boldsymbol{\nabla}T(x)$ and inversely with the damping constant $\alpha$, while the transverse velocity remains negligible. Varying interfacial DMI $D_{int}$, uniaxial anisotropy $K_u$, and saturation magnetization $M_s$ reveals parameter windows where $v_x$ increases sharply but $\theta_{sk}$ stays suppressed, suggesting a robust design principle for Hall-free transport. The results highlight a size-torque interplay and challenge some existing thermal-spin theories, offering a route toward energy-efficient spintronic devices that harvest waste heat for information transport.

Abstract

Thermal gradient driven skyrmion dynamics offers a promising route toward green spintronics, enabling the utilization of waste heat for information transport and processing. Using micromagnetic simulations, we investigate Neel skyrmions in a Co-Pt bilayer nanoracetrack and demonstrate that stochastic torques induced by a thermal gradient drive skyrmion motion toward the hotter region with a nearly vanishing Hall angle. The dynamics depends sensitively on intrinsic material parameters - the skyrmion velocity decreases with increasing damping constant, increases with stronger thermal gradients, and varies systematically with saturation magnetization, interfacial DMI strength, and uniaxial out of plane anisotropy. Importantly, we identify a specific range of material parameters within which the skyrmion velocity changes sharply while the Hall angle remains strongly suppressed, saturating near zero. This comprehensive parameter-dependent study establishes a universal design framework for minimizing the Hall effect in thermal gradient driven spintronic systems.

Figures (5)

• Figure 1: (a) Schematic of the Co/Pt track. (b)-(f) Snapshot of the skyrmion position at different times.
• Figure 2: (a) Representative skyrmion trajectory in racetrack for the $\boldsymbol{\nabla} T{\rm{(x)}}$=0.785 K/nm. (b) $v_{\rm{x}}$ and $v_{\rm{y}}$ as a function of $\boldsymbol{\nabla} T{\rm{(x)}}$. (c) $v_{\rm{x}}$ as a function of damping constant. Inset shows the $v_{\rm{x}}$ vs. $1/\alpha$. Dotted lines are guides to the eyes.
• Figure 3: (a) $v_{\rm{x}}$ and $\theta_{\rm{sk}}$ as a function of $D_{\rm{int}}$ at a fixed thermal gradient $\boldsymbol{\nabla} T_{\rm{x}} = 0.785$ K/nm. (b) $v_{\rm{x}}$ and $\theta_{\rm{sk}}$ as a function of $K_{\rm{u}}$ at the same gradient. In both panels, the red symbols represent the $v_{\rm{x}}$ component, while the black symbols represent $\theta_{\rm{sk}}$. Dotted lines are guides to the eyes.
• Figure 4: $v_{\rm{x}}$ and $\theta_{\rm{sk}}$ as functions of $M_{\rm{s}}$ at a fixed thermal gradient $\boldsymbol{\nabla} T_{\rm{x}} = 0.785$ K/nm. Red symbols represent the $v_{\rm{x}}$
• Figure 5: Variation of skyrmion diameter ($R$), $\theta_{\rm sk}$, and $v_{x}$ (top to bottom) as a function of (a) $D_{\rm int}$, (b) $K_{u}$, and (c) $M_{s}$. Dotted lines are guides to the eyes. Vertical lines indicate the relevant material-parameter thresholds, and horizontal dotted lines mark the corresponding skyrmion-diameter at thresholds.