Mössbauer and vibrational DOS studies of diluted magnetic tin oxides and nano iron oxides

Abstract

The magnetic properties and Mössbauer results for SnO2 doped with 57Fe are reviewed, and the values of isomer shift and quadrupole splitting are compared with the results obtained by ab initio calculations. It is concluded that the exchange interactions between oxygen defects and magnetic atoms are responsible for long range magnetic interactions of dilute Fe ions dispersed in SnO2. Fe atom precipitated clusters may be formed in highly Fe doped SnO2 samples by annealing at relatively high temperatures for several hours. The reduction of the particle size to nano-scale dimensions induces magnetization, which can be associated with oxygen defects. We have measured the nuclear inelastic scattering (NIS) spectra of Fe oxides, and 57Fe and (Co or Mn) doped SnO2 synthesized mainly by sol–gel methods and we have derived the vibration density of states (VDOS). The local phonons are sensitive to the presence of precipitated clusters.