Electron spin resonance (ESR) of magnetic sublattices in Sc-substituted barium hexaferrite

The partial substitution of Fe3+ by Sc3+ in barium hexaferrite has shown to be an effective method to tailor anisotropy for many novel microwave applications. Some basic studies have revealed that this substitution leads to unusual interactions among the magnetic sublattices of the ferrite. In order to investigate these interactions, samples with formula BaScxFe12-xO19 (1 <= x <= 2) were prepared by sintering (1300 degrees C, 6h). After structural characterization by x-ray diffraction, their ferromagnetic resonance spectra were measured in the X-band (9.4 GHz), in the 100-500 K temperature range. For x = 2, a single, broad resonance peak was observed at the low temperatures (103 K), exhibiting a progressive splitting into two peaks for increasing T, to finally coalesce again into a single (paramagnetic) narrow peak at 473 K. These results are interpreted in terms of a substitution of Fe3+ by Sc3+ ions in the 4 f(vi) and 2b sublattices; the diamagnetic cations disrupt the superexchange interactions and produce a splitting of the 12k sublattice (which interacts directly with the 4 f(vi) sublattice) into two sublattices with different canting angles, and different thermal dependence. As a result, the fraction of the 12k sublattices that are nearest neighbours of substituted 4 f(vi) sites can behave as an independent sublattice for some temperature ranges. A similar behavior is observed for all the compositions with varying degrees of amplitude, but it is more evident for x = 2. A deconvolution of peaks has been attempted, in order to shed more light into this behavior. (C) 2016 Author(s).