Observation of Thermal Spin–Orbit Torque in W/CoFeB/MgO Structures

Abstract

Coupling of spin and heat currents enables the spin Nernst effect, the thermal generation of spin currents in nonmagnets that have strong spin−orbit interaction. Analogous to the spin Hall effect that electrically generates spin currents and associated electrical spin−orbit torques (SOTs), the spin Nernst effect can exert thermal SOTs on an adjacent magnetic layer and control the magnetization direction. Here, the thermal SOT caused by the spin Nernst effect is experimentally demonstrated in W/ CoFeB/MgO structures. It is found that an in-plane temperature gradient across the sample generates a magnetic torque and modulates the switching field of the perpendicularly magnetized CoFeB. The W thickness dependence suggests that the torque originates mainly from thermal spin currents induced in W. Moreover, the thermal SOT reduces the critical current for SOTinduced magnetization switching, demonstrating that it can be utilized to control the magnetization in spintronic devices.

A numerical study on the energy barrier for cutting magnetic stripe domains in thin films

“…We will focus on this "change form stripe state to broken stripe" process and its energy barrier. Our findings might provide a fundamental criterion for determining what states could be observed in the presence of thermal fluctuations 25,27,29,[39][40][41][42] .…”

Thermally generated spin current in the topological insulator Bi 2 Se 3

“…Understanding thermally generated spin currents in topological insulators is important for characterizing the effect of Joule heating on measurements of current-induced spin-orbit torques ( 15 ). If the thermal spin currents are sufficiently strong, they could in principle be put to use in generating useful torques ( 16 , 17 ). The Mott relation, which connects the spin Nernst effect to the spin Hall effect, provides insight into the origin of the large effect we measure and also suggests how even stronger thermal-gradient to spin-current conversion might be achieved by optimizing topological insulators.…”