La-Ni Substituted M-type Sr Hexaferrite Studied by ⁵⁷Fe Mössbauer Spectroscopy

Abstract

We have measured the ⁵⁷Fe Mössbauer spectra of Sr_1-xLa_xFe_12-xNi_xO₁₉ (x=0, 0.1 and 0.2) at room temperature using the powder and the single crystalline samples. All observed spectra were well fitted using the five subspectra, which correspond to the five nonequivalent Fe sites. In Sr_1-xLa_xFe_12-xNi_xO₁₉ (x=0.1 and 0.2), the substitutions of Ni²⁺ ions for Fe³⁺ ions are required by the electric charge balance. For SrFe₁₂O₁₉, the relative absorption intensities in the spectrum observed using the single crystalline sample are much different from those observed using the powder one. This result shows large anisotropies of the recoilless fractions at the Fe sites. The refined hyperfine interaction parameters of the 4f₁, 2a, and 2b sites decrease linearly with increasing x. The substitution of a Ni²⁺ ion for a Fe³⁺ ion changes hyperfine interaction parameters by the perturbation of the Fe-O-Ni hybridizations. Accordingly, the Fe ions in the vicinity of the 4f₁, 2a, and 2b sites are replaced by the Ni²⁺ ions.