Effect of Co and Sm Substitutions on the Magnetic Interactions of M-Type Strontium Hexaferrite Nanoparticles

In this contribution, we report the tuning of magnetic properties of Co- and Sm-substituted strontium hexaferrite nanoparticles. Stoichiometric and single-phase strontium hexaferrite (SrM) nanoparticles have been synthesised by sol–gel route using high-purity nitrates. The structural characterisation of synthesised samples was studied by X-ray diffraction studies. The experimental evidence indicates the crystallite size and morphology of nanoparticles. Hysteresis curves of Sr(1−x)SmxFe12O19 (x = 0.1, 0.2 and 0.3) show a significant increase of the coercivity of the samples, as compared with those of SrFe12−xCoxO19 (x = 0.1, 0.2 and 0.3), which depend on the effect of Fe2+ anisotropy on the 2a site in the Sm3+ ions. This effect if resulted in the large magneto crystalline anisotropy and coercive force. Important magnetic properties such as coercivity, remanence, saturation magnetisation, Bohr magneton and squareness ratio and exchange coupling can be tailored by controlling the grain size, composition and density of bulk magnetic materials. At nanometric length scales, the grain size plays an increasingly important role since magnetic domain behaviour and grain boundary concentration determine bulk magnetic behaviour. The temperature dependence magnetic behaviours of the samples were also discussed.