On the magnetic susceptibility of tenorite

This paper reports a theoretical investigation of the perpendicular magnetic susceptibility of a tenorite (CuO) single crystal at absolute zero temperature. We present formulae for the ground state system energy taking into account the exchange interactions, the magnetic anisotropy energy, and the Zeeman energy, as well as expressions for the equilibrium angles. Expressions for the susceptibility tensor components are obtained. The magnetic susceptibility along the arbitrary direction in (ac)-plane is a 180 degrees periodic function of the field directional angle. The magnitude of the projection of the magnetization vector on the field direction depends on the field intensity by the linear law. Pm expression for the flip field is obtained, and a crude numerical estimate of the susceptibility is given. The correctness of the notion of a flip field in the molecular field approximation for the anisotropy energy is discussed. The susceptibility anisotropy is caused by both the g-factor anisotropy and the non-Heisenberg-type exchange interactions. The experimental results are discussed.