Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta

Abstract

We report on a comparative study of spin Hall related effects and magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements allow to estimate the characteristic transport parameters of both Pt and Ta layers juxtaposed to YIG: the spin mixing conductance G ↑↓ at the YIG|normal metal interface, the spin Hall angle ΘSH, and the spin diffusion length λ sd in the normal metal. The inverse spin Hall voltages generated in Pt and Ta by the pure spin current pumped from YIG excited at resonance confirm the opposite signs of spin Hall angles in these two materials. Moreover, from the dependence of the inverse spin Hall voltage on the Ta thickness, we extract the spin diffusion length in Ta, found to be λ Ta sd = 1.8 ± 0.7 nm. Both the YIG|Pt and YIG|Ta systems display a similar variation of resistance upon magnetic field orientation, which can be explained in the recently developed framework of spin Hall magnetoresistance.

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

“…On the other hand, the SMR in the NM has the angular dependence 22 described by Eq. (17). These considerations lead to the parametrization of resistivity by…”

“…In reverse, the inverse spin Hall effect 9,10 (ISHE) can convert the spin current generated by certain means, for instance spin pumping 11,12 , into an electric signal. A particularly intriguing phenomenon that involves both SHE and ISHE is the spin Hall magnetoresistance [13][14][15][16][17][18][19][20][21][22] (SMR), in which a charge current in an NM causes a spin accumulation at the edge of the sample due to SHE, yielding a finite spin current at the interface to a ferromagnet. Through ISHE, the spin current gives an electromotive force along the original charge current, effectively changing the magnetoresistance of the NM.…”