Ponente
Descripción
Hexaferrites (M) are widely used as permanent magnet materials due to their good magnetic behavior and low costs. In the three main types of hexaferrites substitutions with rare earth ions have been reported, although some authors found a limit to their solubility. The study of the coercive field with La substitution has received attention in relation to the high anisotropy field of lanthanum hexaferrite. The results reported are very contradictory, since while there are studies that report improvements in the magnetic properties with these substitutions, others report a scarce variation in these properties. This inconsistency also occurs due to the fact that the studies refer to different methods of obtaining and different dopant ranges, which makes it difficult to compare the different reports. We present a study on ceramic Ba-M hexaferrite doped with La and Gd, so that a wide range of substitutions can be compared, even reaching the solubility limit but also covering the low substitution range. The variation of the anisotropy and coercive fields was studied. A non-monotonic variation of the magnetic properties with substitution was found and then we can report an optimal substitution range. This non-monotonic behavior may also explain the inconsistency of the previous reports. A contradictory behavior between the coercive and anisotropy fields was also found for the highest substitution values.
Keywords: Hexaferrites, Magnetic characterization, Rare earth doping, Coercivity, Magnetization.
