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

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

PHYSICA B - CONDENSED MATTER

Elsevier

Año: 2008

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 = y = 0:2 in the formula Ba1-x Lax Fe12-y Coy O19. In this work, this stoichiometry is initially used to obtain a state where more than one phase is present. The magnetic behavior as a function of temperature was studied in order to have an insight into the magnetic interactions that originate a decrease in the magnetic performance of Ba hexaferrite magnets. The sample was structurally characterized by x-ray diffraction (XRD) and magnetically studied in a SQUID magnetometer. FORC distributions were used to study the dependence of the magnetic interactions with the temperature. FORC diagrams performed on the sample at di®erent 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.