Tb3+ substituted strontium hexaferrites: Structural, magnetic and optical investigation and cation distribution

Abstract

In this study, SrFe12−xTbxO19 (0.00 ≤ x ≤ 0.1) hexaferrites (HFs) were prepared successfully by citrate sol-gel approach. X-ray powder diffraction analyses affirm the hexagonal structure of products. Impurity phase starts to appear for x ≥ 0.04. The crystallites sizes were estimated to be in the range of 33–46 nm. All the products exhibit inhomogeneous distribution of grain size detected through SEM. The analyses of magnetization versus applied magnetic field, M(H), were performed. Magnetization measurements were done at room (300 K; RT) and low (10 K) temperatures. The different magnetic parameters including saturation magnetization Ms, remanence Mr, squareness ratio (SQR = Mr/Ms), coercivity Hc, and magnetic moment nB are deduced and discussed in detail. At both considered temperatures, M(H) results show ferrimagnetic nature for all compositions. It is shown that the Tb substitutions significantly affect M(H) data. A significant increase in the Ms, Mr, and nB is observed for x = 0.02 sample. The SQR values are around 0.5 indicating the single domain nature with uniaxial anisotropy. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties. Mössbauer spectroscopy results were also investigated. According to Mössbauer results, the Tb3+ ions preferentially occupy 12k and 4f2 sites.