Here, we focus on ferromagnetic ordering in as-deposited and ultrahigh vacuum (UHV) annealed Co-doped ITO films using magnetometry together with XAS and XMCD. The annealing process is found to increase the saturation magnetization but decrease the magnetic moment per Co ion.
XAS and XMCD measurements were performed over the Co [L.sub.2,3] edges (2p [right arrow] 3d dipole transitions) on beamline 106, Diamond Light Source, using the UHV compatible superconducting high-field magnet which provides fields of up to 6 T and operates in a temperature range of 2-370 K.
The presence of metallic Co in the annealed Co-doped ITO sample was also confirmed by XAS and XMCD spectra measured in FY mode and is shown in Figure 5.
To probe the origins of the magnetism in the annealed films further, XAS and XMCD measurements were performed at 4 K and at remanence.
The rise in magnetization upon UHV annealing should therefore be largely ascribed to defects introduced during the formation of metallic Co clusters, as evidenced by changes in the XAS and XMCD spectra as well as the blocking temperature in the magnetization versus temperature response.
Corresponding XMCD spectra for (d) Co metal, (e) as-deposited Co-doped ITO, and (f) annealed Co-doped ITO.
(b) XMCD spectra for the as-deposited (black line) and annealed (red line) Co-doped ITO film.