Program Highlights

Hydroxyl-Induced Magnetism in TiO Nanoclusters

David J. Sellmyer, Xiao Chen Zeng, and Ralph Skomski
Nebraska MRSEC

Dilute magnetic oxides are interesting for fundamental science and applications in spintronics. A main  challenge in understanding the defect ferromagnetism in dilute magnetic oxides is the direct experimental verification of the presence of a particular kind of defect and distinguishing its magnetic contributions from other defects. Nebraska MRSEC researchers have studied the magnetic effect of hydroxyls on TiO nanoclusters by measuring the evolution of the magnetic moment as a function of moisture exposure time, which increases the hydroxyl concentration. Using first-principles calculations dealing with OH^- on TiO(110) they showed that the atomic moments are confined to surface and subsurface Ti atoms and that the moments are exchange-coupled over several interatomic distances [Nanoscale 4, 7704 (2012)].

This work illustrates the essential interplay between defect structure and magnetism. This is important both technologically and scientifically because it helps to understand the puzzling question why dilute magnetic oxides are magnetic at room temperature, in spite of their very small net moment.

These programs are supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant 0820521.

Hydroxyl creation at oxygen vacancies on TiO (left) and hydrogen adsorption on a relaxed TiO surface of a defective nanocrystal, as determined by DFT calculations (right).