Studying the magnetic characteristics of strontium-substituted gadolinium ferromanganite by the method of Mossbauer spectroscopy and electron paramagnetic resonance

Background. Multiferroics of rare-earth manganites RMnO$_{3}$ attract a lot of attention due to the significant correlation between the electrical and magnetic ordering parameters. The replacement of rare-earth ions in RMnO$_{3}$ with atoms of a different radius and / or valence leads to the appearance of new effects, such as colossal magnetoresistance, and various thermomagnetic effects. These phenomena are usually associated with magnetic separation in the subsystem of magnetic moments - the formation of microregions of ferromagnetic ordering in an antiferro- or paramagnetic matrix. When studying this phenomenon, it is promising to use the methods of Mossbauer spectroscopy and electron paramagnetic resonance (EPR), which make it possible to reliably record the presence of magnetic impurities of the order of fractions of a percent. Materials and methods. Strontium-substituted gadolinium ferromanganite Gd$_{0.82}$Sr$_{0.18}$Mn$_{0.9}$Fe$_{0.1}$O$_{3}$ was prepared by ceramic technology. Its magnetic microstructure was investigated by the method of Mossbauer spectroscopy at temperatures of 67-300 K and EPR at temperatures of 100-340 K. Results. The experimental data of Mossbauer and EPR measurements indicate the magnetic phase separation of magnetic moments in strontium-substituted gadolinium ferromanganite. Conclusions. Analysis of the Mossbauer spectra shows the presence of one quadrupole doublet, whose isomeric shift corresponds to Fe$^{3+}$ ions, and a superposition of two Zeeman sextets, which tell us about the separation of the magnetic subsystem. The EPR spectra were approximated by three lines L$_{1}$, L$_{2}$, and L$_{3}$. Two lines correspond to ferromagnetic clusters, which are observed in a paramagnetic matrix at temperatures exceeding the Néel temperature, and the other is associated with manganese and iron ions in the paramagnetic state. A similar behavior of the magnetic subsystem was observed in the ceramics Eu$_{0.65}$Sr$_{0.35}$Mn$_{1-x}$Fe$_{х}$O$_{3}$ with x=0.2, 0.25.