Magnetic properties and phase diagram of ZnxNi1−xFe2O4: High-temperature series expansions

Using mean field theory and high-temperature series expansions (HTSEs), extrapolated with the Padé approximants method, the effect of Zn doping on magnetic properties of NiFe₂O₄ ferrite spinel has been studied. The nearest neighbour super-exchange interactions for intra-site (J_AA, J_BB) and inter-site (J_AB) of the Zn_xNi_1−xFe₂O₄ ferrites spinels, in the range 0≤x≤1, have been computed using the probability approach, based on Mössbauer data. The paramagnetic Curie-Weiss temperature θ and the Curie temperature T_C are calculated as a function of Zn concentration. The critical exponent γ associated with magnetic susceptibility is calculated. The spin correlation functions intra-plane and inter-plane have been also computed and compared with exchange couplings. The obtained theoretical results are in good agreement with experimental ones obtained by magnetic measurements and Mössbauer spectroscopy.