Hydrogen mediated ferromagnetism in ZnO single crystals

TL;DR

This study demonstrates that hydrogen plasma treatment induces ferromagnetism in ZnO single crystals, with magnetic properties localized near the surface and correlating with hydrogen concentration, achieving room-temperature ferromagnetism.

Contribution

It provides experimental evidence of hydrogen-induced ferromagnetism in ZnO and characterizes its dependence on hydrogen concentration and surface localization.

Findings

Ferromagnetism localized within 20 nm of the surface

Saturation magnetization up to 6 emu/g at 300 K

Curie temperature exceeds 400 K

Abstract

We investigated the magnetic properties of hydrogen plasma treated ZnO single crystals by SQUID magnetometry. In agreement with the expected hydrogen penetration depth we found ferromagnetic behavior located at the first 20 nm of the H-treated surface of ZnO with magnetization at saturation up to 6 emu/g at 300 K and Curie temperature T$_c$ $\gtrsim $ 400 K. In the ferromagnetic samples a hydrogen concentration of a few atomic percent in the first 20 nm surface layer was determined by nuclear reaction analysis. The saturation magnetization of H-treated ZnO increases with the concentration of hydrogen.