Thermally-driven spin torques in layered magnetic insulators

Abstract

Thermally-driven spin-transfer torques have recently been reported in electrically insulating ferromagnet$|$normal-metal heterostructures. In this paper, we propose two physically distinct mechanisms for such torques. The first is a local effect: out-of-equilibrium, thermally-activated magnons in the ferromagnet, driven by a spin Seebeck effect, exert a torque on the magnetization via magnon-magnon scattering with coherent dynamics. The second is a nonlocal effect which requires an additional magnetic layer to provide the symmetry breaking necessary to realize a thermal torque. The simplest structure in which to induce a nonlocal thermal torque is a spin valve composed of two insulating magnets separated by a normal metal spacer; there, a thermal flux generates a pure spin current through the spin valve, which results in a torque when the magnetizations of the layers are misaligned.

7 pages, 4 figures

References in corpus (5)

• Spin Seebeck insulator
• Thermal Spin-Transfer Torques in Magnetoelectronic Devices
• Interfacial Spin and Heat Transfer between Metals and Magnetic Insulators
• Dynamic phase diagram of dc-pumped magnon condensates
• Magnon instability driven by heat current in magnetic bilayers

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• Planar Hall torque
• Spin caloritronic nano-oscillator
• Two-Fluid Theory for Spin Superfluidity in Magnetic Insulators
• Bose-Einstein Condensation of Quasi-Particles by Rapid Cooling
• Magnon Valves Based on YIG/NiO/YIG All-Insulating Magnon Junctions
• Spin conductance of YIG thin films driven from thermal to subthermal magnons regime by large spin-orbit torque
• Strain-Tuned Magnetic Anisotropy in Sputtered Thulium Iron Garnet Ultrathin Films and TIG/Au/TIG Valve Structures
• Bose-Einstein Condensation of Magnons Pumped by the Bulk Spin Seebeck Effect
• Spin current cross-correlations as a probe of magnon coherence
• Probing thermal magnon current mediated by coherent magnon via nitrogen-vacancy centers in diamond
• Local thermomagnonic torques in two-fluid spin dynamics
• Electrically induced strong modulation of magnons transport in ultrathin magnetic insulator films
• Damping of parametrically excited magnons in the presence of the longitudinal spin Seebeck effect
• Non-local magnon transconductance in extended magnetic insulating films.\\Part II: two-fluid behavior