Investigation of Magnetic Properties of Sr-Doped Ba_3–xSr_xCo₂Fe₂₄O₄₁ Z-type Hexaferrite by Mössbauer Spectroscopy

摘要

The polycrystalline BaSrCoFeO (, and 1.5) samples were synthesized by the solid-state reaction method. The crystalline structure of the samples was found to be a hexagonal structure with a space group of . The lattice constants , , and of the samples decrease with increasing Sr concentration. From the field-dependent hysteresis curves under 10 kOe at 295 K, the values of increase while the values of decrease. The zero-field-cooled magnetization curves under 100 Oe between 4.2 and 300 K show the spin transition, and the value of decreases from 230 K for to 135 K for with increasing Sr concentration due to the reduction of planar anisotropy with the difference in ionic radius between Ba and Sr ions. From the isomer shift value () obtained from Mössbauer spectra, the charge states of all samples are determined to be Fe high spin state. With increasing Sr concentration, the reduction of hyperfine field