First order reversal curves analysis of the temperature effect on magnetic interactions in barium ferrite with La–Co addition

OLIVA, M. I.; BERCOFF, P.G.; BERTORELLO, H. R.

PHYSICA B - CONDENSED MATTER

ELSEVIER SCIENCE BV

Año: 2009 vol. 404 p. 2742 - 2745

0921-4526

First order reversal curves (FORC) distributions are a powerful tool for investigating hysteresis and interactions in magnetic systems and have been widely applied. La-Co substitution in barium hexaferrites has also been extensively studied . The most effective substitution to improve the magnetic properties (coercive field and energy product) is given by x = 0.2 in the formula Ba1-x Lax Fe12-x Cox O19, so this stoichiometry is used in this work  to prepare a sample and study its magnetic behavior as a function of temperature. The sample was structurally characterized by x-ray diffraction (XRD) and magnetically studied in a SQUID magnetometer. The temperature effect on the magnetic properties of a Ba0.8 La0.2 Fe11.8 Co0.2 O19 was analyzed by conventional ZFC-FC and magnetization M vs. applied field H curves. FORC distributions were used to study the dependence of the magnetic interactions with the temperature.  FORC diagrams performed on the sample at different temperatures exhibit similar characteristics, such as the spread in the hc - hu plane and a spread out of the hc axes. These features are interpreted in terms of exchange-interacting particles and dipolar interactions, respectively. As the temperature decreases, stronger interactions are noticed among hard and soft phases.