6. Nonequilibrium cation influence on the Néel temperature in ZnFe2O4,

I. AL-OMARI; H. WIDATALLAH; F. R. SIVES; S. J. STEWART

Buenos Aires

Congreso; International Symposium on Metastable and Nanostructured Materials; 2008

The nonequilibrium distribution of cations in ZnFe2O4 brings about changes in its magnetic ordering that goes from antiferro, cluster-glass to ferrimagnetic state as the inversion, i.e., the fraction (c) of tetrahedral A sites occupied by iron, increases [1-2]. Ordered (normal, c=0) ZnFe2O4 has a AF order with a  Néel temperature TN = 10 K. A ferrimagnetic ordering has been reported to occur in disordered nanosized ZnFe2O4 below TN460-490 K. The study of the magnetism of disordered ZnFe2O4 has been mainly focused on its low temperature behavior and, to our knowledge, only one work has reported on its magnetization above ambient conditions [3]. Objective: To investigate how the ordering temperature TN depends on the inversion or particle size. To this aim, we present results on the temperature dependence above room temperature of the magnetization of ZnFe2O4 nanoferrites having different degree of inversion and sizes. Our results and others from the literature are compared with theoretical predictions by assuming a random distribution of superexchange interactions.