Effect of heat-treatment on the magnetic and optical properties of Sr_0.7Al_0.3Fe_11.4Mn_0.6O₁₉

Sr_0.7Al_0.3Fe_11.4Mn_0.6O₁₉ was synthesized by sol-gel technique and sintered at varying temperatures 750 °C, 850 °C, 950 °C and 1050 °C for 5 h. We investigate the role of heat-treatment on the structural, magnetic and optical properties of Al–Mn doped strontium hexaferrite. XRD analysis indicates the formation of M-type hexaferrites with some traces of α-Fe₂O_3. The presence of two prominent peaks between 400 cm⁻¹ and 600 cm⁻¹ in the spectra of FTIR gives the possibility of the emergence of M-type hexagonal ferrites. FESEM micrograph shows that the grains of the prepared sample possess Plate-like hexagonal structure. EDX spectra confirmed the stoichiometry of the prepared sample. Recrystallization of the synthesized sample and formation temperature of 650 °C is observed in TGA analysis. Variation of the sintering temperature results in decrease of the band gap. Magnetic parameters were calculated from the M–H loop obtained from vibrating sample magnetometer (VSM). High value of coercivity (6750 Oe) is observed at 850 °C. Remanent and saturation magnetization decreases with increase heat-treatment temperature. The synthesized sample may be useful in perpendicular recording medium (PRM) and high frequency application. (paper)