Cr-doped TiO2 (rutile): Ferromagnetism in bulk form?

Abstract

Cr-doped rutile samples in powder and single crystal form have been prepared and studied with particular emphasis on their compositional, structural, and magnetic properties. Both powders and single crystals were characterized using x-ray diffractometry and vibrating sample magnetometry, while crystals were also studied using the x-ray Laue technique, scanning electron microscopy, and energy dispersive x-ray analysis. The results indicate weak ferromagnetic behavior at room temperature (RT) in Cr-doped TiO2 powders having 2 at. % Cr, while powders with higher amounts of Cr (e.g., 8 or 12 at. %) showed no evidence of ferromagnetism. Following successful floating zone crystal growth of Cr-doped rutile crystals in argon, magnetic measurements taken from the as-grown crystals revealed no indication of RT ferromagnetism over the composition range 2 to 12 at. % Cr. A solubility limit for Cr into the rutile matrix of 3 at. % Cr at RT is suggested.