Crystallization and Mössbauer Studies of Y3-xLaxFe5O12 (x=0.0, 0.25, 0.5, 0.75, 1.0)

Abstract

Magnetic and structural properties of garnet Y3-xLaxFe5O12(x= 0.0, 0.25, 0.5, 0.75, 1.0) have been studied by using X-ray diffraction, Mossbauer spectroscopy, and vibrating sample magnetometer. Polycrystalline cubic powders have been prepared by a metal-salt routed sol-gel method. Mossbauer spectra of Y3-xLaxFe5O12 have been taken at various temperatures ranging from 12 to 700 K. The lattice parameter increases linearly with increasing La concentration and follows Vegard's law approximately. Magnetic hyperfine fields of Y2.5La0.5Fe5O12 at 12 K are found to be 543 kOe (octahedral site) and 469 kOe (tetrahedral site). The values of the isomer shifts show that all of iron ions are in the ferric (Fe+3). The Curie temperature. Tc, is found to depend strongly upon La concentration. i.e., 578 K for x=0 and 625 K for x=0.5. The dependence of the Curie temperature suggests that the strengthen of superexchange interaction by La-O-Fe link is stronger than that by Y-O-Fe link.