Abstract:
In this work, the magnetodielectric response have been studied in a series of single crystals of Pb$_2$Fe$_{2-x}$Mn$_x$Ge$_2$O$_9$ with substitution x from 0 to 0.43. The research results showed that an increase in $x$ leads to a change in the orientation of the antiferromagnetism vector in a zero magnetic field. The application of an external magnetic field leads to spin-flop and spin-reorientation magnetic transitions, which are accompanied by anomalies in the behavior of the permittivity.When Fe$^{3+}$ ions are replaced by Mn$^{3+}$ ions, the response of the magnetic subsystem to an external magnetic field changes, which is naturally reflected in the change in the magnetodielectric response. The permittivity changes stepwise when the magnetic subsystem passes into a state with a nonzero vector of the weakly ferromagnetic moment, or when its magnitude and orientation change due to a spin-flop transition. The latter indicates that a sharp change in polarizability is a consequence of a change in the contribution of the exchange energy, as well as the contribution of the Dzyaloshinskii–Moriya term, due to a change in the skew angle between two interacting magnetic moments.
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