Metastable giant moments in Gd-implanted GaN, Si, and sapphire

TL;DR

This study investigates Gd ion implantation in GaN, Si, and sapphire, revealing giant magnetic moments and metastable ferromagnetism, supporting a defect-based mechanism for magnetism in these materials.

Contribution

It demonstrates the existence of giant magnetic moments in Gd-implanted GaN, Si, and sapphire and explores their metastability, providing new insights into defect-induced magnetism.

Findings

Gd ions exhibit giant magnetic moments up to 1800 μ_B in GaN.

Metastable ferromagnetism persists for about 50 days at room temperature.

Magnetic moments are consistent across different host materials.

Abstract

We report on Gd ion implantation and magnetic characterization of GaN films on sapphire substrates and of bare sapphire and Si substrates to shed light on the mechanism underlying the induced magnetism upon Gd ion implantation. For all three hosts, giant magnetic moments per Gd ion were observed at temperatures of 5 through 300 K. The maximum moment per Gd in GaN was 1800 mu_B, while the moments in Gd-implanted Si and sapphire were only slightly smaller. The apparent induced ferromagnetic response was found to be metastable, disappearing after on the order of 50 days at room temperature, except for the implanted sapphire. We argue that our findings support a defect-based picture of magnetism in Gd-implanted semiconductors and insulators.