Estudi d'algunes ferrites hexagonals uniaxials

by Isalgue Buxeda, Antoni

ABSTRACT: The aim has been the understanding of phenomena giving rise to the magnetic ordering and magnetocrystalline anisotropy in uniaxial hexaferrites. Measurements of X-ray and neutron diffraction (to refine structure and magnetic ordering), magnetization as function of temperature (to obtain magnetization to saturation with the law of approach to saturation, and magnetocristalline anisotropy with the singular point detection), and Mössbauer spectroscopy (to determine the behaviour of Fe3+ in different places of structure), have been done. For the M ferrite BaFe12O19, structural data has allowed the computation of dipolar interactions among ionic spins, justifying magnetocrystalline anisotropy at low temperatures. Exchange interactions among Fe3+ have been obtained from Mössbauer data as function of temperature, explaining the magnetic behaviour as function of temperature. The results explain the behaviour of LaZnFe11O19 and the series SrFe12-xCrxO19 for x less than 8. The properties of the R-structure BaMn2Fe4O11 are coherent with the properties of the M structure. KEYWORDS: Solid state physics, Magnetic materials, Hexagonal ferrites, Magnetocristalline anisotropy, Mössbauer spectroscopy, Neutron and X-ray diffraction