Dose dependence of ferromagnetism in Co-implanted ZnO

TL;DR

This study investigates how varying cobalt implantation doses affect the structural, magnetic, and electronic properties of ZnO films, revealing dual magnetic phases and evidence of intrinsic ferromagnetism at room temperature.

Contribution

It provides a detailed analysis of the dose-dependent ferromagnetism in Co-implanted ZnO, identifying two magnetic phases and demonstrating intrinsic ferromagnetism through element-specific magnetization and Hall effect measurements.

Findings

Room temperature ferromagnetism depends on cobalt dose.

Presence of ferromagnetic and superparamagnetic phases.

Evidence of intrinsic ferromagnetism via magnetic dichroism and Hall effect.

Abstract

We have studied the structural, magnetic and electronic properties of Co-implanted ZnO (0001) films grown on Al2O3 (1120) substrates for different implantation doses and over a wide temperature range. Strong room temperature ferromagnetism is observed with magnetic parameters depending on the cobalt implantation dose. A detailed analysis of the structural and magnetic properties indicates that there are two magnetic phases in Co-implanted ZnO films. One is a ferromagnetic phase due to the formation of long range ferromagnetic ordering between implanted magnetic cobalt ions in the ZnO layer, the second one is a superparamagnetic phase, which occurs due to the formation of metallic cobalt clusters in the Al2O3 substrate. Using x-ray resonant magnetic scattering, the element specific magnetization of cobalt, oxygen and Zn was investigated. Magnetic dichroism was observed at the Co L2,3 edges as well as at the O K edge. In addition, the anomalous Hall effect is also observed, supporting the intrinsic nature of ferromagnetism in Co-implanted ZnO films.