Effect of Co-doping Calcium and Scandium on Strontium Hexaferrite: Structural, Magnetic and Mossbauer Study.

M-type hexaferrite such as barium hexaferrite (BaM) and strontium hexaferrite (SrM), have a wide range of applications because of its high saturation magnetization, coercivity and remanance values. The magnetic properties of such materials can be altered for better performance by replacing either magnetic or non-magnetic ions at different lattice sites. The presence of Sr1-x/12Cax/12Fe12-xScxO19 (x = 0.0 to 2.0) hexaferrite (SrM) compounds. The samples were prepared via a facile auto-combustion technique followed by sintering. X-ray powder diffraction patterns show the formation of the pure phase of M-type hexaferrite for all x. Lattice parameters, both a and c of the compound increased with the substitution. The magnetic property of these compounds is explained based on Sc3+ occupancy in M-type magnetoplumbite structure. Both saturation magnetization and coercivity decreased with x. The temperature and field-dependent mangetization study (10-300K) revealed spin reorientation transition and change in magnetic anisotropy energy. The curie temperature dropped to 580K at the maximum substitution of x=2. The room temperature Mossabauer spectral analysis confirmed the preferred occupancy of Sc3+ at the 4f2 site and influence of Ca2+ on the isomer shift values of the 2b site. Changes in magnetic properties and hyperfine parameters are discussed in light of the preferred occupancy of Sc3+ at the spin-down 4f2 site