Spin-Transfer Effects in Structures with Different Magnetic Configurations

Helmholtz Zentrum Dresden-Rossendorf, High Magnetic Field Laboratory

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Since their initial prediction in 1996, spin-transfer induced or assisted phenomena have become one of the most relevant fields in magnetism, with valid industrial applications. Briefly, a spin-polarized current flowing through a ferromagnet exerts a torque on its magnetization at the nanoscale, thereby providing a means of manipulating it. In a nanosized magnet, spin-transfer torques can induce either magnetization reversal or steady-state precession. These phenomena can be exploited to design a range of devices ranging from more obvious applications, such as embedded magnetic memory (currently in production by several companies), to a more distant potential implementation as wireless radio-frequency oscillators for mobile communications, which could potentially cover the terahertz range, or for neuromorphic computing. 

Currently, there remain countless aspects being investigated, from the very applied to the very fundamental. I will focus on fundamental issues, while still connecting to application-related requirements. The talk will cover experimental, theoretical, and micromagnetic analysis of spin-transfer driven precession in MgO-based tunnel junctions, versus basic metallic nanopillars, and spin-transfer switching and precession in junctions with non-collinear magnetization configurations. Other fundamental topics that I will briefly address include the potential of almost compensated ferrimagnets as active layers for spin-transfer driven oscillators in the terahertz range and whether thermal gradients naturally occurring in asymmetric structures, such as the nanopillars used for spin-torque devices, can be functionalized to assist torques induced by direct electrical bias, as predicted by ab-initio calculations.