Exploration of structural, Mössbauer, and hysteresis performance metrics of SrCo x Zn x Fe 12−2x O 19 hexaferrite for recording applications

The present study aims to improve the magnetic properties with tunable coercivity of SrM hexaferrite by substituted Co and Zn ions instead of Fe and to elucidate in detail the changes in their structural, morphological, and site occupancy characteristics. Sr Co_x Zn_x Fe_12 - 2xO_19 (Co, Zn; x = 0.4, 0.8, 1.2, 1.6 and 2.0) powders were synthesized by the autocombustion sol–gel method. Substitution of Co–Zn ions caused the formation of magnetoplumbite and a secondary phase (CoFe 2 O 4 ) in the structure. Increasing the Co–Zn content ratio led to a nonlinear increment in crystallite size ranging from 41.9 to 49.8 nm. SEM micrographs depicted platelet-shaped hexagonal particles that were nano-scale in thickness and micro-scale in diameter. Mössbauer spectra revealed that the substituent tends to occupy both spin-up sites 12k-2a-2b and spin-down sites 4 f 1 and 4 f 2 of crystal lattice from x = 0.4 to x = 2.0, which elucidate meagre change observed in magnetization, as per literature. The saturation magnetization ( M s ) and remanent magnetization ( M r ) were higher than the initial values of M s = 75.26 emu/g and M r = 26.95 emu/g. The highest coercivity and saturation magnetization was observed as, 4159 Oe and 80 emu/g, respectively, for x = 2.0. The squareness ratio ( M r / M s ) of x = 1.6 and x = 2.0 samples, was observed to be greater than 0.5, elucidating the existence of single-domain particles. The magnetic parameters M s with tunable H c , M r / M s , and magnetic susceptibility (d M/ d H ) results make the synthesized sample considerable for recording applications.