Spontaneous magnetoelectric effects in cubic ferromagnetoelectrics

The interrelationship between the orientations of the spontaneous polarization and spontaneous magnetization in ferro(ferri)magnetoelectric crystals with a centrosymmetric cubic paraelectric phase whose ferroelectric transition temperature is lower than the critical temperature for the magnetic ordering is studied. Exact solutions are obtained for the equilibrium moments for any values of the energy parameters. It is shown that the magnetoelectric interaction determines the direction of the electric polarization in a magnetic domain. At lower temperatures first- or second-order phase transitions induced by the magnetoelectric interaction can lead to the reorientation of the moments. As a result of the appearance of the polarization, the magnetization may undergo a 45° deflection in a coordinate plane, or change its orientation from alignment along a coordinate axis to alignment along the cube body diagonal (e.g., ⟨001⟩ ⟶⟨111⟩).

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