Analysis on magnetic field dependence of magneto-optical Faraday effect

In this paper, the complicated relations between Faraday rotation and external magnetic field in various circumstances are theoretically deduced using magneto-optical four-level model. A linear field dependence of the Faraday rotation in extremely strong magnetic field or at high temperatures is revealed. Our theory also shows that the Faraday rotation presents an obvious nonlinear field-dependence property in a general magnetic field and at low temperatures. Furthermore, this nonlinear relationship can be simply described as theta(F)=theta(Fs)+aH(e)+bH(e)(2). In addition, a fit to the experimental results in Dy(3-x)Bi(x)Fe(5)O(12) (Bi-DyIG) under different magnetic fields is obtained. Meanwhile, it is pointed out that the parameters V(1) and V(2) have the anisotropy and temperature-dependence characteristic, which will also result in the anisotropic and temperature properties of magneto-optical Faraday effect in Bi-DyIG. (C) 2008 American Institute of Physics.