Enhanced spin pumping at yttrium iron garnet/Au interfaces

Abstract

Spin injection across the ferrimagnetic insulator yttrium iron garnet (YIG)/normal metal Au interface was studied using ferromagnetic resonance. The spin mixing conductance was determined by comparing the Gilbert damping parameter α in YIG/Au and YIG/Au/Fe heterostructures. The main purpose of this study was to correlate the spin pumping efficiency with chemical modifications of the YIG film surface using in situ etching and deposition techniques. By means of Ar+ ion beam etching, one is able to increase the spin mixing conductance at the YIG/Au interface by a factor of 5 compared to the untreated YIG/Au interface.

Spin-Hall magnetoresistance in platinum on yttrium iron garnet: Dependence on platinum thickness and in-plane/out-of-plane magnetization

“…More notable, the e-beam evaporated Pt layer on YIG did show only a very low SMR signal (≈10 −5 ). This suggests that the spin-mixing conductance (which is determined by the interface) 19 is an important parameter for the occurrence of SMR.…”

Modulation of pure spin currents with a ferromagnetic insulator

“…One could take advantage of the spin-mixing conductance concept [5,6] at nonmagnetic metal (NM)/ferromagnetic insulator (FMI) interfaces, which governs the interaction between the spin currents present at the NM and the magnetization of the FMI. This concept is the basis of new spindependent phenomena, including spin pumping [6][7][8][9][10][11][12], spin Seebeck effect [6,13], and spin Hall magnetoresistance (SMR) [6,[14][15][16][17][18]. In these cases, a NM with large spin-orbit coupling is required to convert the involved spin currents into charge currents via the inverse spin Hall effect [19].…”

“…The difference, which is less than a factor of 2, can thus be considered to be small, taking into account that, in order to observe a relevant variation in β, a much larger change in G r is needed [Fig. 4(c [16], and Au/YIG (between 3.5 × 10 13 and 1.9 × 10 14 −1 m −2 ) [10,11] either by SMR or spin pumping experiments.…”

“…Such effects are unlikely in Cu/YIG. It is worth noting that the G r of a NM/YIG interface, for a NM with a negligible spin-orbit coupling, was not experimentally measured before due to the need of the inverse spin Hall effect (and thus a high spin-orbit coupling metal) in the experiments made so far [6][7][8][9][10][11][12][13][14][15][16].…”

Effect of quantum tunneling on spin Hall magnetoresistance

“…This approach solves the spin diffusion equation in the presence of SHE and ISHE in a self-consistent manner, where the spin current at the NM/FMI interface serves as a boundary condition. However, the interface spin current remains an external parameter for which experimental or numerical input is needed 23,24 . On the other hand, a quantum tunneling formalism has emerged recently as an inexpensive tool to calculate the interface spin current from various material properties such as the insulating gap of the FMI and the interface s − d coupling 26 .…”