Crystallization and Mossbauer Studies of Y_<3-x>La_xFe_5O_<12>(x=0.0,0.25,0.5,0.75,1.0)

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Magnetic and structural properties of garnet Y_<3-x>La_xFe_5O_<12>(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 Y_<3-x>La_xFe_5O_<12> 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 Y_<2.5>La_<0.5>Fe_5O_<12> 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 irons are in the ferric (Fe^<+3>). The Curie temperature, T_c, 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.
社団法人日本磁気学会の論文
1999-01-20