Characterization of Continuous Wave Laser-Induced Thermal Gradients in Magnetic Tunnel Junctions Integrated Into Microresonators via COMSOL Simulations

Spin caloritronics investigates static and dynamic effects on magnetic structures due to spin-currents generated by thermal gradients. Here, we present COMSOL simulation results using a 2-D heat transfer module applied to Co₂FeAl/MgO/CoFeB magnetic tunnel junctions (MTJs) integrated into microcavity resonators. Microresonators are used in order to study the effects of temperature gradients on single micro-/nano-objects. We find that the thermal conductivity of the insulating barrier (MgO) plays a crucial role, influencing the overall temperature, as well as the thermal gradient over the barrier. Taking into account the microresonator structure around the MTJ, which is mainly made from copper, strongly affects the uniform heating of the overall stack. Nevertheless, the gradient over the barrier is relatively unaffected by the surrounding conditions. The simulation results provide insight into the temperature profile of the whole structure and show how modifying the structure of the surrounding materials may tune and optimize the thermal gradient magnitude and ultimately provide a path for quantifying spin-transfer torques induced by thermal gradients.