Hydrogen-induced ferromagnetism in ZnO single crystals investigated by Magnetotransport

TL;DR

This study demonstrates that hydrogen implantation in ZnO single crystals induces ferromagnetism and modifies electrical properties, showing potential for magnetic and electronic applications.

Contribution

It reveals that hydrogen atoms alone can induce magnetic order in ZnO, offering a simple method to generate ferromagnetism in this material.

Findings

Ferromagnetic hysteresis observed at 300 K with saturation magnetization up to 4 emu/g.

Anomalous Hall effect consistent with magnetometry measurements.

Negative magnetoresistance and non-monotonous anisotropic magnetoresistance behavior.

Abstract

We investigated the electrical and magnetic properties of low-energy hydrogen-implanted ZnO single crystals with hydrogen concentrations up to 3 at.% in the first 20 nm surface layer between 10 K and 300 K. All samples showed clear ferromagnetic hysteresis loops at 300 K with a saturation magnetization up to 4 emu/g. The measured anomalous Hall effect agrees with the hysteresis loops measured by superconducting quantum interferometer device magnetometry. All the H-treated ZnO crystals exhibited a negative magnetoresistance up to the room temperature. The relative magnitude of the anisotropic magnetoresistance reaches 0.4 % at 250 K and 2 % at 10 K, exhibiting an anomalous, non-monotonous behavior and a change of sign below 100 K. All the experimental data indicate that hydrogen atoms alone in a few percent range trigger a magnetic order in a ZnO crystalline state. Hydrogen implantation turns out to be a simpler and effective method to generate a magnetic order in ZnO, which provides interesting possibilities for future applications due to the strong reduction of the electrical resistance.