All-Semiconducting Spin Filter Prepared by Low-Energy Proton Irradiation

We report on a spin filter effect that emerges at potential barriers between a ≃10 nm thick magnetic surface layer and nonmagnetic regions prepared at the surface of Li-doped ZnO microwires by low-energy H+-ion implantation. The spin filter effect manifests in a large positive magnetoresistance that persists to room temperature, is linear in magnetic field, shows a maximum around 30 K, scales linearly with the number of successive potential barriers created along the microwires, and vanishes when the potential barrier is absent. The specific features of the observed effect can be reproduced with a model that describes a spin-polarized transport through a potential barrier acting as a minority spin filter with an efficiency Psf > 10% at room temperature and Psf = 100% at 10 K.