Mössbauer spectroscopy on the magnetic hyperfine interaction of nonstoichiometric europium iron garnet

Abstract

The microscopic physical properties of the nonstoichiometric garnet Eu1−xFe1+xO3(x=0.2) have been studied by using X-ray diffraction at room temperature and M¨ossbauer spectroscopy within the temperature range from liquid nitrogen temperature to 560 K. The X-ray diffraction patterns of the sample show coexistence of dominant garnet and a small portion of an unknown crystal phase. However, the M¨ossbauer spectrum for the sample near the N´eel temperature, which was 549±5 K, shows that, within experimental errors, there were no other crystal phases. The average area ratio of a- to d-sites for the sample was 0.76, which implies the possibility of some vacancies exsisting at the a- and/or the d-sites. The temperature dependence of the magnetic hyperfine fields was analyzed by using the spin-wave theory and the molecular-field model. From the analysis, the average strength of the interaction and the molecular-field coefficients were determined to be 37.484 K and (−60.0, 95.5, −29.8)(mole/cm3), respectively. From the relations among molecular-field coefficients, the ion distribution at the a- and the d-sites was {Eu3}[Fe1.95](Fe2.82)O12.