Abstract
Thermal-current induced electron and spin dynamics in solids –dubbed “caloritronics”– have generated widespread interest in both fundamental physics and spintronics applications. Here, we examine the dynamics of nanometric topological spin textures, skyrmions driven by a temperature gradient ∇T or heat flow, that are evaluated through in-situ real-space observations in an insulating helimagnet Cu2OSeO3. We observe increases of the skyrmion velocity and the Hall angle with increasing ∇T above a critical value of ~ 13 mK/mm, which is two orders of magnitude lower than the ∇T required to drive ferromagnetic domain walls. A comparable magnitude of ∇T is also observed to move the domain walls between a skyrmion domain and the non-topological conical-spin domain from cold to hot regions. Our results demonstrate the efficient manipulation of skyrmions by temperature gradients, a promising step towards energy-efficient “green” spintronics.
Highlights
Thermal-current induced electron and spin dynamics in solids –dubbed “caloritronics”– have generated widespread interest in both fundamental physics and spintronics applications
Recent research reveals the role of temperature in the dynamics of topological spin textures:[13] the nonlinearly increasing Hall effect as a function of the skyrmion velocity in the low-drive regime close to the depinning threshold; the current-induced the deformation of skyrmion shape from a regular circle to an irregular one in the high-drive regime
The hexagonal skyrmion lattice (SkL) can be generated under the specific fields and temperatures, as exemplified by an over-focus Lorentz transmission electron microscopy (TEM) image taken at 20 K under a normal magnetic field of 60 mT (Fig. 1b)
Summary
Thermal-current induced electron and spin dynamics in solids –dubbed “caloritronics”– have generated widespread interest in both fundamental physics and spintronics applications. In analogy to current-driven spin texture motions[10,11], temperature-gradient-induced magnetization dynamics have been reported in metallic systems via spin-transfer torque on magnetic domain walls[12]. The electric current exerts a force on the skyrmions via spin-transfer torque or spin-orbit torque, resulting in a complicated interaction between spin textures and heat current These complex thermal effects have been demonstrated by recent work on the temperature gradient-driven skyrmion diffusion in a metallic multi-layer film[14]. A temperature gradient can drive magnetic textures in insulating ferromagnets (FM)[15,16] via the transfer of spin angular momentum of the thermally induced magnon current, similar to the conduction electron spin-transfer torque mechanism in metallic FM. The Q is the skyrmion number (integer topological charge), as defined by
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