Mössbauer studies of magnetic anisotropy for BaFe12-2xCoxZrxO19

Abstract

The magnetic anisotropy of BaFe12-2xCoxZrxO19, with x = 0-1.2 has been studied using Mössbauer spectra. Co and Zr ions are found to occupy the 12k and 2b sites preferentially. The quadrupole splittings suddenly decrease in magnitude and are even opposite in sign for the sample of x = 1.2, as compared to other samples. The angle factor, b = A2.5/A3.4, are found to be 0.41 and 0.25 for x = 0 and 0.4, but 1.41 for x = 1.2. These indicate that Co-Zr substitution can modify the anisotropy of BaFe12-2xCoxZrxO19. A general formula of b is derived for nonfully aligned samples with the hexagonal structure by introducing the Gaussian-distribution of magnetic moments to a alignment direction. From the formula, the values of b are calculated to be 4/3 and zero for fully aligned samples with easy c-plane and easy c-axis anisotropies, respectively. In addition, the mean deviation of alignment is also obtained.