Mössbauer and magnetic studies of the phase state of SrFe$_{12}$O$_{19}$/La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ composites

The formation of an intermediate phase in SrFe$_{12}$O$_{19}$/La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ composites was demonstrated for the first time using only Mössbauer spectroscopy. The SrFe$_{12}$O$_{19}$/La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ composite was prepared by the two-stage (sol–gel and hydrothermal) synthesis with varying initial conditions. The X-ray diffraction studies showed that the composite consisted of two phases: well-formed structures of manganite La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ and hexagonal ferrite SrFe$_{12}$O$_{19}$. It was found that nanocrystalline La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ particles with size $d\lesssim$ 150 nm formed in the composites at the surface of plate-like SrFe$_{12}$O$_{19}$ crystallites. The Mössbauer studies showed that the composite contained additional (intermediate) phase La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ that formed at the interface between SrFe$_{12}$O$_{19}$ and La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ phases. The intermediate phase concentration increased with the molar content of La$_{0.9}$Ca$_{0.1}$MnO$_{3}$; in this case, the fraction of the surface of SrFe$_{12}$O$_{19}$ crystallites coated with La$_{0.9}$Ca$_{0.1}$MnO$_{3}$ increased, which led to the increase in the total area of the interface surface and the intermediate phase concentration.