Bulk and Surface Magnetization of Co atoms in Rutile Ti_[1-x]Co_xO_[2-delta] Thin Films Revealed by X-Ray Magnetic Circular Dichroism

TL;DR

This study investigates the magnetic properties of Co-doped TiO2 thin films using XMCD, revealing differences between surface and bulk magnetization and suggesting an intrinsic ferromagnetic origin with a surface dead layer.

Contribution

The paper provides detailed measurements of surface and bulk magnetization in Co-doped TiO2 thin films, highlighting the intrinsic ferromagnetism and surface effects.

Findings

Bulk ferromagnetic moment ranges from 0.82 to 2.25 μB/Co.

Surface ferromagnetic moment is significantly smaller, 0.15-0.24 μB/Co.

Evidence of a magnetically dead surface layer a few nanometers thick.

Abstract

We have studied magnetism in Ti_[1-x]Co_xO_[2-\delta] thin films with various x and \delta by soft x-ray magnetic circular dichroism (XMCD) measurements at the Co L_[2,3] absorption edges. The estimated ferromagnetic moment by XMCD was 0.15-0.24 \mu\beta/Co in the surface, while in the bulk it was 0.82-2.25 \mu\beta/Co, which is in the same range as the saturation magnetization of 1.0-1.5 \mu\beta/Co. Theseresults suggest that the intrinsic origin of the erromagnetism. The smaller moment of Co atom at surface is an indication of a magnetically dead layer of a few nm thick at the surface of the thin films.