Abstract
We evaluated an intrinsic α in ferromagnetic (FM)/non-magnetic (NM) junctions from first principles (FM = Co, Fe, and Ni and NM = Cu, Pd, and Pt) to investigate the effects of the inserted NM layer. α is calculated by liner muffin-tin orbital methods based on the torque-correlation model. We confirmed that Gilbert damping is enhanced and saturated as NM thickness increases, and that the enhancement is greater in NM materials having a stronger spin-orbital interaction. By contrast, the calculated FM thickness dependences of α show that Gilbert damping tends to decrease and be saturated as the FM thickness increases. Under the torque-correlation model, the dependences of α on FM and NM thickness can be explained by considering the electronic structure of the total system, including junction interfaces, which exhibit similar behaviors derived by spin pumping theory.
Highlights
Research and development of recent magnetic devices have garnered much interest in the mechanism and control of spin relaxation, as demands for high speed and low consumption power, in spintronics devices such as magnetic random access memory and others, have increased
The variation of α for NM thickness is large in the order of Pt, Pd, and Cu, which indicates that the NM layers act as a spin sink through their spin-orbit interaction (SOI)
From the torque-correlation model using the first-principle linear muffin-tin orbital (LMTO) method, we evaluated the NM and FM thickness dependence of α at various FM/NM junctions
Summary
Research and development of recent magnetic devices have garnered much interest in the mechanism and control of spin relaxation, as demands for high speed and low consumption power, in spintronics devices such as magnetic random access memory and others, have increased. In 2009, Kambersky[1] and Gilmore et al.[2,3] proposed a calculation method of α as an effect of spin-orbit interaction (SOI) within the framework of the first principles electronic structure calculation. Based on this theory, α of many transition metal systems have been calculated both for ordered and disordered alloys.[4,5]. The origins of the distinctions are not clear at this stage, experiments[6,7] and theories[8] showed that an additional term exists that results from spin flows from magnetic layers to non-magnetic (NM) layers in magnetic multilayered systems, which is currently recognized as a spin pumping mechanism. The spin pumping phenomena are free from SOI and originate from inhomogeneous spin structures[9] including magnetic multilayered systems, which lead to the migration of spin angular moments
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