Mössbauer studies of Y-type hexaferrite with aluminum doping

Abstract

The crystal structures of polycrystalline Ba2Co1.5Mg0.5(Fe1−xAlx)12O22 (x = 0.00, 0.01, 0.02) samples were determined to be rhombohedral with a space group of R−3m. From the temperature-dependent magnetization curves under 100 Oe, all samples showed helimagnet-to-ferrimagnet transitions. Based on the applied-field-dependent magnetization measurements up to 10 kOe at 295 K, the saturation magnetization (Ms) and coercivity (Hc) of Ba2Co1.5Mg0.5(Fe1−xAlx)12O22 (x = 0.00, 0.01, 0.02) samples were found to be Ms = 28.0, 24.7, 23.4 emu/g and Hc = 255.4, 222.0, 196.2 Oe, respectively. Also, from the Mossbauer spectra of 295 K, the isomer shift values of all samples indicate charge states of Fe3+. We expect that the decrease in the Ms with increasing Al ion doping is due to the fact that Al ions preferentially occupy the 3bV I, 18hV I and 3aV I octahedral sublattices, which are up-spin sites.