Synthesis of Co-Zr doped nanocrystalline strontium hexaferrites by sol-gel auto-combustion route using sucrose as fuel and study of their structural, magnetic and electrical properties

Sol-gel auto-combustion route using sucrose as fuel has been employed to synthesize nanocrystalline particles of SrZrxCoxFe(12−2x)O19 (0.0≤ x ≤1.0). The characterization of these materials has been done by TGA-DTA, FT-IR, XRD and EDS. SEM and TEM techniques have been used to study the structure and morphology. Magnetic properties have been investigated by VSM and Mössbauer spectroscopy (MS). The influence of calcination temperature on morphology and magnetic properties of samples is studied in a wide temperature range of 500-1100 °C. XRD analysis indicates the formation of pure single phase hexagonal ferrites at 900 °C. The crystallite size calculated using Scherrer equation lies in a narrow range of 21-33 nm. The crystallite size is small enough to obtain a suitable signal to noise ratio in high density recording medium. Substitution of Zr and Co for Fe has been found to have a profound effect on the structural, magnetic and electrical properties. Upon substitution saturation magnetization (MS) first increases from 62.67 emu/g to 64.84 emu/g (up to x=0.4) followed by a decrease to 49.71 emu/g at x=1.0. There is a slow fall in coercivity (HC) from 5785.74 (x=0.0) to 1796.51 Oe (x=1.0). Dielectric constant, dielectric loss tangent and AC conductivity in the frequency range 20 Hz to 120 MHz have been studied for all the compositions (x=0-1.0). The composition and frequency dependence of these dielectric parameters has been qualitatively explained.