Pure spin current transport in gallium doped zinc oxide

TL;DR

This study demonstrates that pure spin currents can propagate through gallium-doped zinc oxide layers, with the spin Hall magnetoresistance decreasing but remaining finite even at 12 nm thickness, influenced by interface resistances.

Contribution

It provides experimental evidence of pure spin current transport through doped zinc oxide and highlights the importance of interface resistances in spin diffusion models.

Findings

SMR magnitude decreases with interlayer thickness

Pure spin current propagates through several nanometers of Ga:ZnO

Interface resistances significantly affect SMR magnitude

Abstract

We study the flow of a pure spin current through zinc oxide by measuring the spin Hall magnetoresistance (SMR) in thin film trilayer samples consisting of bismuth-substituted yttrium iron garnet (Bi:YIG), gallium-doped zinc oxide (Ga:ZnO), and platinum. We investigate the dependence of the SMR magnitude on the thickness of the Ga:ZnO interlayer and compare to a Bi:YIG/Pt bilayer. We find that the SMR magnitude is reduced by almost one order of magnitude upon inserting a Ga:ZnO interlayer, and continuously decreases with increasing interlayer thickness. Nevertheless, the SMR stays finite even for a $12\;\mathrm{nm}$ thick Ga:ZnO interlayer. These results show that a pure spin current indeed can propagate through a several nm-thick degenerately doped zinc oxide layer. We also observe differences in both the temperature and the field dependence of the SMR when comparing tri- and bilayers. Finally, we compare our data to predictions of a model based on spin diffusion. This shows that interface resistances play a crucial role for the SMR magnitude in these trilayer structures.