Antiferromagnetic resonance and phase diagrams of gadolinium ferroborate GdFe3(BO3)4

The antiferromagnetic resonance in the monocrystals of the GdFe3(BO3)4 rhombohedral gadolinium ferroborate is studied. The frequency-field dependences of the antiferromagnetic resonance within the frequency range of 26-70 GHz and temperature dependences of the resonance parameters for the magnetic field oriented along the crystal axis and in the base plane are investigated. It is established that at the T = 38 K there takes place the ordering of the iron subsystem which may be presented as the two-sublattice antiferromagnetic with the anisotropy of the light plane type. Strong effect on the anisotropic properties of the gadolinium subsystem crystal having the opposite anisotropy sign is identified at the temperature below 20 K. This effect at T = 10 K results in the spontaneous spin-reorientation transition from the light-plane to the light-axis state. Transitions between the states induced by the magnetic field are identified below 10 K. The experimental phase diagrams are plotted on the temperature-magnetic field plane for the fields oriented along the crystal axis and in the base plane. The transitions critical fields coinciding well with the experimental values measured at T 4.2 K for both field orientations are calculated within the simple model frames