Equality of diagonal and non-diagonal microwave susceptibilities of EuO

The two elementsχ′ _yx andχ″ _xx of the magnetic susceptibility tensor for the cubic ferromagnetic EuO are investigated at microwave frequencies. It is shown that these two elements coincide when the magnetic field is large enough to remove the domain structure within the sample. This is in coincidence with theoretical predictions and shows a certain structure of the Hamiltonian. The magnetic transition temperature is found to beT _c=(69.2±0.2)°K in agreement with the result from specific heat measurement.