Enhanced spin accumulation obtained by inserting low-resistance MgO interface in metallic lateral spin valves

Abstract

We have systematically investigated the interface contributions to the spin injection characteristics in permalloy/MgO/Ag lateral spin valves. The spin valve signal remarkably increases with MgO thickness and reaches a maximum when the interface resistance is about 100 f⍀ m 2 for 1 nm thick MgO, which is two orders of magnitude lower than that of the typical tunnel junction. Our quantitative analysis based on the spin-dependent diffusion equation considering variable spin polarization in the MgO layer well describes the observed trend in the spin valve signals.

Large Spin Accumulation with Long Spin Diffusion Length in Cu/MgO/Permalloy Lateral Spin Valves

“…The maximum spin accumulation voltage becomes about 10 V at 10 K. From the spin accumulation signals as a function of distance (d) between the two Py wires, we obtain the spin diffusion length of Cu ( N ) as 1.3 m and the spin polarization (P F ) of Py as 0.26 at 10 K. This spin diffusion length is about two times larger than that of Ag reported in ref. 13. Using the two values (i.e., N ¼ 1:3 m and P F ¼ 0:26), we can also explain the R I dependence of the spin accumulation signal up to R I ¼ 3:0 Â 10 À1 (m) 2 .…”

Spin transport enhancement by controlling the Ag growth in lateral spin valves

“…Lateral spin valves (LSVs) are basic spintronic devices that offer an attractive means to study the spin transport as well as the spin injection properties in different materials. After the pioneering studies, first by Johnson and Silsbee [2,3] and more recently by Jedema et al [4,5], a large number of spin injection experiments have been reported in metals [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], semiconductors [23,24] or carbon-based materials [25,26]. LSVs consist of two ferromagnetic (FM) electrodes, used to inject and detect pure spin currents, bridged by a non-magnetic (NM) channel, which transports the injected spin current (see Fig.…”

“…For the optimum performance of a LSV, it is crucial to choose a NM material in which the spin information can travel over long distances, i.e. with long spin diffusion length λ NM , with Cu [4-12], Al [2,5,9,13,14] or Ag [15][16][17][18][19][20][21][22] being the most commonly selected metals. In order to enhance λ NM , it is crucial to understand which are the spin relaxation processes that lead to the loss of spin information.…”

Spin pumping blocked by single-layer graphene

“…Insertion of an oxide or Schottky barrier into the F=SS junction further reduces J sd , causing the exponential decay of the spin pumping efficiency observed in a recent experiment. [8][9][10] SLG has been found to work as an insulating interlayer to prevent impedance mismatch between a ferromagnetic metal and a semiconductor; [24][25][26] thus, the suppression of spin pumping observed in the present study is attributed mainly to the reduction in the spin-exchange coupling at the F=SS interface. In addition, because the spin resistance of SLG is much larger than those of Ni 81 Fe 19 and Pt, the insertion of SLG prevents the effective transfer of spin currents at the interface, which can also contribute to the suppression of spin pumping in the present system.…”