Non-equilibrium cation influence on the Neel temperature in ZnFe2O4

We present results on the thermal dependence of the magnetization above ambient conditions of ZnFe2O4 nanoferrites having different degrees of inversion (c similar to 0 05-0 40) and grain sizes (D similar to 6-50 nm) The disordered ferrites present a net magnetization in the 400-510K range that mainly depends on the degree of inversion. The reciprocal magnetization deviate from different temperature values of the linear behavior showed at high temperatures. Our results show that, contrary to similar nanoferrite systems, a simple scaling law cannot be applied to explain the Neel temperature T-N dependency with the grain size These results can be interpreted in terms of the lack of correlation between size and inversion that occurs in ZnFe2O4 and the strong T-N dependence on the superexchange J(AB) interaction strength A model assuming a random distribution of superexchange interactions can reproduce the Curie-Weiss temperature and the saturation magnetization values of the disordered ferrites. (C) 2009 Elsevier B V. All rights reserved.