Study of structural transformation and hysteresis behavior of Mg-Sr substituted X-type hexaferrites

Abstract

Effect of Mg-Sr substitution on thermal, structural, spectral, dielectric and magnetic properties were explored in the X-type hexagonal ferrites having composition of Ba2-xMgxCo2-ySry Fe28O46 (x = y = 0, 0.1, 0.2, 0.3, 0.4, 0.5) synthesized via a sol-gel auto-combustion process. The sintered material was characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), dielectric measurement and vibrating sample magnetometer (VSM) techniques. The sintering temperature necessary for the entire degradation of nitrates and the hexagonal phase development was found 1250 °C which was determined from thermo-gravimetric analysis. The formation of the single phase hexagonal was confirmed from XRD patterns. The lattice constants and cell volume were found to be decreased. This decreased was attributed to the lower ionic size of the substituted metal ions. The porosity of the synthesized material was found to be decreased from 0.463 to 0.417 with the increase in the substitution. FTIR spectroscopy of Mg-Sr doped material revealed the characteristics absorption bands of hexa-ferrites and it was investigated in the frequency range of 400–1000 cm−1. The dielectric measurement has been explored as the function of frequency and composition. Ac conductivity was found to be increased from 1.46 to 2.029 Ω cm−1. The Cole-Cole graphs of prepared materials revealed the promising role of grain boundaries in the conduction mechanism. The improvement in the coercivity was observed with the increase in the Mg-Sr cations, while the saturation magnetization was decreased with the increase in the substitution. The higher value of the coercivity of these synthesized material proposed their use in longitudinal recording media.