Spontaneous magnetization of amorphous ferromagnets with anisotropy

The mean field approximation was used to calculate by iteration (for simple cubic lattices of up to 1728 spins) the spontaneous magnetization of a spin one ferromagnet in which the amorphousness is simulated by fluctuating the magnitude of the uniaxial anisotropy term (of strength D and average value D). Fluctuations with D=0 as well as about a positive value of D were considered. Nearest neighbor (n.n) Ising exchange interactions with periodic boundary conditions were used. In the approximation considered, each spin interacted withe the local mean field created by its 6 n.n.’s and it also experienced a randomly fluctuating uniaxial anisotropy. Generally, the fluctuations caused a decrease in the magnetization from the crystalline mean field case. For D=0 convergence problems were encountered near the Curie temperature. By examining both the free energy and the magnetization it is shown that increasing D suitably higher values of D, there is no thermodynamically stable magnetized state. The magnetiza...