Synthesis, structural and magnetic properties of ZnxMg1−xFe2O4 nanoferrites

ZnxMg1−xFe2O4 nanoparticles (0≤x≤1 in steps of 0.1) have been produced by centrifugation using the low temperature glycol-thermal method at 200 °C. Single-phase formation was confirmed by X-ray powder diffraction which revealed a well-defined cubic spinel structure with space group Fd3m. HRTEM and TEM were also used for the morphology studies. The crystallite size of the compounds ranged from 10.6 to 22.2 nm. A strong correlation was found between X-ray density and Zn-concentration, x. The magnetic properties as a function x were investigated by using 57Fe Mössbauer spectroscopy, magnetization measurements using a Lakeshore vibrating sample magnetometer (VSM) at room temperature. We also report VSM measurement on a cryogen free measurement system at isothermal temperatures between 4 K and 300 K in external applied magnetic fields of up to 5 T. For x<0.8, the room-temperature Mössbauer results show that the samples were transformed from paramagnetic state to magnetic ordered state. The temperature-dependences of saturation magnetization and coercive field follow the modified Bloch's law and Kneller's law, respectively. Strong correlation between saturation magnetization MS(0) and crystallite size D is observed. Two distinct composition ranges with Zn content are identified for which MS(0) variation with x is explained by the Néel and Yafet-Kittel models.