Cation distribution in the europium iron garnet series Eu3Fe5-xA1xO12.

Abstract

The cation distributions in europium iron garnet Eu3Fe5 5-xAlxO12 series have not been determined yet since they were synthesized and studied by Yamaguchi and Sakuraba twenty years ago. In this thesis, the Fe-Al distributions over the octahedral ( a) and tetrahedral (d) sites in the europium iron garnet Eu3Fe5-xAlxO12 series have been determined by powder X-ray diffraction (XRD) and 57Fe Mossbauer spectroscopy (57Fe MS). The 57Fe MS spectra are collected at temperatures above the Neel temperatures of the studied samples and the cation distributions are derived from both the raw and thickness-corrected MS spectra. It is found that Al atoms occupy both the a and d sites. Higher Al concentration in the d sites is interpreted as the evidence that Al atoms enter preferentially the d sites due to the smaller size of Al ions compared with Fe ions. MS gives more reliable results of the Fe-Al distributions than XRD, which could be ascribed to the sensitivity of MS to the local environment around the iron nucleus at the specific site.