Magnetic and Mössbauer Effect Study of Ca-Sc Co-doped M-Type Strontium Hexaferrite

The present study investigates the influence of Ca 2+ -Sc 3+ co-dpoing on the magnetic properties of Sr 1-x/12 Ca x/12 Fe 12-x Sc x O 19 ( x = 0.0 to 2.0) hexaferrites. The samples were prepared via a facile autocombustion technique followed by sintering in ambient air. X-ray powder diffraction patterns show the formation of the pure phase of M-type hexaferrite. The lattice parameters a and c increased with the Ca 2+ -Sc 3+ doping. The compounds’ magnetic properties were assessed as a function of temperature (10–300 K) and field (up to 6T). A rapid decline in room temperature coercivity from 5458 to 373 Oe and remanence value from 37 to 13 emu/g and a moderate decline in saturation magnetization from 76.9 to 57 emu/g were observed with increasing doping content from x = 0.0 to 2.0. The phase transition temperature, corresponding to ferrimagnetic to conical, was observed below 100 K, which disappeared at low doping content. The temperature-dependent behavior of magnetization and coercivity is discussed in view of spin non-collinearity due to the change in magnetic anisotropy. The Curie temperature dropped from 769 K at x = 0 to 568 K at the maximum substitution of x =2.0. The room temperature Mossbauer spectral analysis confirmed the preferred occupancy of Sc 3+ at the 4 f 2 site and the influence of Ca 2+ on the isomer shift values of the 2 b site. The increased quadrupole shift values with the substitution implied distortion in 2 b bipyramidal symmetry. The observed changes in magnetic properties and hyperfine parameters are ultimately tied to the preferred occupancy of Sc 3+ at the spin-down 4 f 2 site.