Magnetic properties of the noncollinear phase of a FeBO3:Mg single crystal

The magneto-optical method is used to investigate magnetization and low-frequency magnetic susceptibility curves of the FeBO3 single crystal doped with diamagnetic Mg ions. It is demonstrated that substitution of a fraction of Fe ions by the Mg ions in the structure of this easy-plane weak ferromagnet causes a significant intraplane magnetocrystalline anisotropy at low temperatures as well as different forms of magnetic hysteresis loops and field dependences of the magnetic susceptibility recorded for different orientations of the external magnetic field relative to the basal crystal plane. The established special features of the FeBO3:Mg magnetic properties are explained by the transition of the magnetic crystal from the uniform to spatially modulated state during technical magnetization.