High temperature ferromagnetism in Co-implanted TiO2 rutile

TL;DR

This study demonstrates room-temperature ferromagnetism in Co-implanted TiO2 rutile, revealing two magnetic phases: substitutional Co 2+ ions causing ferromagnetism and metallic cobalt clusters causing superparamagnetism.

Contribution

It provides detailed analysis of magnetic phases and element-specific magnetization in Co-implanted TiO2, highlighting the coexistence of ferromagnetic and superparamagnetic behaviors.

Findings

Room-temperature ferromagnetism observed in Co-implanted TiO2

Presence of both substitutional Co 2+ ions and metallic cobalt clusters

Element-specific magnetic dichroism detected at Co L and O K edges

Abstract

We report on structural, magnetic and electronic properties of Co-implanted TiO2 rutile single crystals for different implantation doses. Strong ferromagnetism at room temperature and above is observed in TiO2 rutile plates after cobalt ion implantation, with magnetic parameters depending on the cobalt implantation dose. While the structural data indicate the presence of metallic cobalt clusters, the multiplet structure of the Co L3 edge in the XAS spectra gives clear evidence for a substitutional Co 2+ state. The detailed analysis of the structural and magnetic properties indicates that there are two magnetic phases in Co-implanted TiO2 plates. One is a ferromagnetic phase due to the formation of long range ferromagnetic ordering between implanted magnetic cobalt ions in the rutile phase, and the second one is a superparamagnetic phase originates from the formation of metallic cobalt clusters in the implanted region. Using x-ray resonant magnetic scattering, the element specific magnetization of cobalt, oxygen and titanium in Co-implanted TiO2 single crystals are investigated. Magnetic dichroism was observed at the Co L edges as well as at the O K edge. The interaction mechanism, which leads to ferromagnetic ordering of substituted cobalt ions in the host matrix, is also discussed.