Mössbauer spectroscopy studies of phase evolution in SrFe12O19/La0.5Ca0.5MnO3 composites

A composite system composed of SrFe12O19 (SFO) and La0.5Ca0.5MnO3 (LCMO) was prepared by a two-stage sol-gel/hydrothermal synthesis technique. Starting conditions were varied to obtain products with 1:1 and 1:2 M ratios of SFO:LCMO. The morphology and composition of the composites were characterized by SEM and room-temperature Mössbauer spectroscopy, revealing the growth of nanocrystalline La0.5Ca0.5MnO3 particles (d ⩽ 150 nm) on the surface of SrFe12O19 platelets. Mössbauer spectra not only confirm the presence of well-formed M-type hexagonal ferrite in the composite materials, but also demonstrate the formation of a new, intermediate phase La0.5Ca0.5Mn(Fe)O3 at the interface between SFO and LCMO. The signature of the intermediate Fe-containing phase increases with the starting molar content of La0.5Ca0.5MnO3, as a greater fraction of the SrFe12O19 surface is covered by La0.5Ca0.5MnO3, increasing the total interfacial area. The trends in coercivity in the series of samples between 10 K and 300 K are reported and discussed in terms of sample morphology.