Magnetic properties of ZnxFe3−xO4 nanoparticles: A competition between the effects of size and Zn doping level

Abstract

Abstract The nanoparticles of the ZnxFe3−xO4 (0\u202f≤\u202fx\u202f≤\u202f0.5) ferrites have been synthesized using a simple co-precipitation method under air atmosphere at room temperature. The Fourier transform infrared spectroscopy and X-ray diffraction patterns confirm the formation of spinel mono-phase structure in all the samples. The results show that the crystallite size relates to the cationic distribution. The cation distribution is derived from the X-ray diffraction patterns enabling determination of ion coordination, ion occupancy and unit cell parameter. The magnetic hysteresis loops reveal that the magnetization increases with Zn content up to x\u202f=\u202f0.3 and then decreases with further Zn doping, which is explained in terms of the competition between the influence of crystallite size and cations distribution (site occupancies). The thermal behavior of magnetization for the selected x\u202f=\u202f0.3 sample is described by a modified Bloch law, based on the spin wave excitations in the particle core. Furthermore, the temperature of the AC magnetic susceptibility peak increases up to 0.3 Zn, then decreases by further Zn doping. The frequency dependence of AC magnetic susceptibility indicates the presence of strong interparticle interactions resulting in a superspin glassy state. The experimental evidence of memory effect in x\u202f=\u202f0.3 sample further confirms the frustrated magnetic state in the compounds. The potential application of these materials for hyperthermia based therapy has been estimated. The results show that in the studied series, Zn0.3Fe2.7O4 with highest loss power is the best candidate for this therapy.