Orbital Moment Determination In (Mnxfe1-X)(3)O-4 Nanoparticles

Nanoparticles of (MnxFe1-x)(3)O-4 with a concentration ranging from x = 0 to 1 and a crystallite size of 14-15 nm were measured using X-ray absorption spectroscopy and X-ray magnetic circular dichroism to determine the ratio of the orbital moment to the spin moment for Mn and Fe. At low Mn concentrations, the Mn substitutes into the host Fe3O4 spinel structure as Mn2+ in the tetrahedral A-site. The net Fe moment, as identified by the X-ray dichrosim intensity, is found to increase at the lowest Mn concentrations then rapidly decrease until no dichroism is observed at 20% Mn. The average Fe orbit/spin moment ratio is determined to initially be negative and small for pure Fe3O4 nanoparticles and quickly go to 0 by 5%-10% Mn addition. The average Mn moment is anti-aligned to the Fe moment with an orbit/spin moment ratio of 0.12 which gradually decreases with Mn concentration. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562905]