Magnetic, dielectric, and magnetoelectric phenomena accompanying low-temperature magnetic transitions in gdfeo3

A number of new features in the magnetic, magnetoelectric, and magnetodielectric properties of the GdFeO3 orthoferrite at phase transitions induced by a magnetic field H || a, b, c at low temperatures have been detected. A threefold increase in the permittivity in the form of peaks during spin-flip transitions in the Gd subsystem, which is accompanied by the suppression of the spontaneous electric polarization, as well as dielectric anomalies at a spin-reorientation (spin-flop) transition induced by the magnetic field H || a in the Gd and Fe subsystems in both ferroelectric $(T < T_{{\text{N}}}^{{{\text{Gd}}}})$ and paraelectric $(T > T_{{\text{N}}}^{{{\text{Gd}}}})$ phases, has been established. In the magnetic field H || c, below the magnetization compensation point, it has been found that an unusual transition occurs due to the reversal of the spontaneous weak-ferromagnetic moment of Fe from the direction against the magnetic field to the direction along the field and is accompanied by a break in its antiferromagnetic coupling to the Gd magnetic moment induced by the magnetic field. A proposed theoretical model including the exchange interactions allowed by symmetry and the magnetoelectric coupling has made it possible for the first time to consistently describe the temperature and field dependences of the permittivity and electric polarization.