Annealing-induced enhancement of ferromagnetism and nano-particle formation in ferromagnetic-semiconductor GeFe

TL;DR

This study demonstrates that annealing enhances ferromagnetism and induces nano-particle formation in GeFe, significantly increasing its Curie temperature and improving its potential for high-temperature spin-injection applications.

Contribution

It reveals how annealing temperature controls phase formation and magnetic properties in GeFe, achieving near-room-temperature ferromagnetism in nano-particles.

Findings

Curie temperature increased to ~220 K after annealing below 500°C

Formation of GeFe nano-particles with high Curie temperature at 600°C

Annealing effectively improves magnetic properties for spin-injection devices

Abstract

We report the annealing-induced enhancement of ferromagnetism and nano-particle formation in group-IV-based ferromagnetic-semiconductor GeFe. We successfully increase the Curie temperature of the Ge0.895Fe0.105 film up to ~220 K while keeping a single ferromagnetic phase when the annealing temperature is lower than 500{\deg}C. In contrast, when annealed at 600{\deg}C, single-crystal GeFe nano-particles with stacking faults and twins, which have a high Curie temperature nearly up to room temperature, are formed in the film. Our results show that annealing is quite effective to improve the magnetic properties of GeFe for high-temperature-operating spin-injection devices based on Si or Ge.