Structure and magnetism of nanocrystalline and epitaxial (Mn,Zn,Fe)_3O_4 thin films

摘要

Nanocrystalline (NC) textured Mn_(0.5)Zn_(0.6)Fe_(1.9)O_4 (MZFO) films, grown at room temperature on both isostructural and non-isostructural substrates, show magnetization values significantly suppressed from epitaxial MZFO films. X-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements indicate larger ratios of Fe~(3+) to Fe~(2+) ions on the tetrahedral sites in the NC films compared to the epitaxial films. The magnetization loops of the NC films are shifted by 200-400 Oe at low temperatures. No such effect is observed in the epitaxial films. We hypothesize that the presence of a more structurally disordered, possibly magnetically frustrated, matrix exchange biases the crystalline regions.