Weak ferromagnetism along the third-order axis of the FeBO3 crystals caused by Fe2+ impurity ions

Using the single-ion approximation, the weak ferromagnetic moment σ_Z(Fe²⁺) along the third-order axis of FeBO₃ crystals, which is caused by the contribution of Fe²⁺ ions, has been investigated in the framework of the model Fe²⁺ impurity ion –BO₃ vacancy. The extreme low-temperature behavior of the total magnetic moment due to the strong dependence of the Fe²⁺ion contribution is predicted.