Transverse Ferromagnetic Resonance of Heisenberg Ferromagnets With Exchange Anisotropy

The effect of oscillating magnetic field on the anisotropic susceptibility of a spin S = 1/2 anisotropic three-dimensional Heisenberg ferromagnet, is studied by the double-time Green's function method within Tyablikov approximation. The results show that the magnetic resonant frequencies directly and sensitively depend on the exchange anisotropic constant (α), and the directions of applied magnetic field. In the case of transverse oscillating field, the transverse susceptibilities exhibit strong resonant effect, and the positions of resonant frequency are sensitive and change monotonically to α. However, in the case of longitudinal oscillating field, the longitudinal susceptibilities are rather flat and display no resonant effect. Therefore, transverse ferromagnetic resonance is a precise technique to measure the magnitude of α, and this conclusion is very useful in the alloy multilayer application.