Non-equilibrium cation influence on the Néel temperature in ZnFe2O4

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

JOURNAL OF ALLOYS AND COMPOUNDS

ELSEVIER SCIENCE SA

Año: 2010 vol. 495 p. 506 - 508

0925-8388

Wepresent results on the thermal dependence of the magnetization above ambient conditions of ZnFe2O4 nanoferrites having different degrees of inversion (c approx. 0.05–0.40) and grain sizes (Dapprox. 6–50 nm). The disorderedferrites 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 behaviorshowed at high temperatures. Our results show that, contrary to similar nanoferrite systems, a simple scaling law cannot be applied to explain the Néel temperature TN 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 TN dependence on the superexchange JAB 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.