[7p-PB7-1~56] 10 スピントロニクス・マグネティクス（ポスター）

▲ [7p-PB7-9] Effect of normal metal seed and capping layers on the magnetization dynamics of permalloy thinfilms

〇(P)Satya Prakash Pati¹、Yasushi Endo¹ (1.Tohoku Univ.)

キーワード：Permalloy, Magnetization Dynamics, FMR

Study of spin transport across normal metal/ ferromagnet/normal metal (NM/FM/NM) has attracted enormous interest after exploitation of spin pumping, inverse spinHall effect like phenomena for applications in MRAM, magnetic data storage and spin-logic. Spin current (J_{S, pump}) generated from a precessing magnetization of a FM injects into both adjacent NM and dissipates under the influence of strong spin orbit interaction (SOI) resulting in an enhancement of damping parameter due to loss of angular momentum is known as spin pumping. Dissipation of J_{S, pump} depends on the material properties of NM can be parameterized as spin mixing conductance. There are many ongoing debates on the other external parameter effecting J_{S, pump} dissipation induced Gilbert damping e.g. interfacial spin resistance, proximity induced spin polarization, magnetic dead layer at interface etc. Herein, we evaluate the magnetization dynamics in a various thick permalloy (Py) film with both NM seed and capping layers (Pt or Cu), and discuss in detail the effect of NM seed and capping layers on the dynamics of Py thin films. The Gilbert damping parameter as a function of Py layer thickness was investigated for Py thin films with NM seed and capping layers(NM=Cu and Pt). In case of NM=Cu, damping parameter almost remains constant when Py layer thickness decreases. Their values are a little larger than those of bare Py thin films, and are approximately 0.015 - 0.017.On the other hand, in case of NM=Pt,damping parameter increases remarkably from 0.012 to 0.046 when Py layer thickness decreases. The differences between Cu and Pt layers can be explained as the spin diffusion length(L_SF): In case of NM=Cu, L_SF is larger than a Cu layer thickness and hence spin mixing inside Cu is negligible resulting in no change of damping parameter. However, in case of NM=Pt, L_SF is shorter than a Pt layer thickness, so J_{S, pump} fully relax within Pt layer and hence damping parameter is enhanced. In addition, the enhancement of damping parameter for Pt case can be attributed to the enhanced electron-magnon scattering as electron accumulation can occur at the Py/Pt interface.Therefore, this result reveals that the spin diffusion length of NM seed and capping layer plays an important role with the magnetization dynamics of Py thin film.