Magnetostatic critical point phenomena of ErIGa garnet

The magnetostatic critical point phenomena of an ErIGa garnet, Er-3(Fe0.8Ga 0.2)(5)O-12, single crystal sphere were investigated by a computer controll ed vibrating sample magnetometer. Subtracting the induced large spin parama gnetic moment of Er3+ from the measured values, allowed the Fe-sublattice m agnetization M-sub(H,T) to be extracted. M-sub data were used to analyze th e critical phenomena by eliminating the low held data to avoid the effect o f the magnetic inhomogeneity. The spontaneous magnetization and the zero-fi eld susceptibility were obtained from the Arrot plot, The critical temperat ure and critical indices were obtained to be T-c = 463.64 K, beta = 0.48+/- 0.03, gamma = 1.1 +/- 0.1, and delta = 3.1 +/- 0.1. These results agree wel l with the predicted values from the molecular field theory. The plot of th e critical equation of states psi(H,M) showed the same function as that fou nd for Fe. Thus, M-sub(H,T) was shown to satisfy the second-order phase tra nsition based on the molecular field theory. (C) 1998 American Institute of Physics. [S0021-8979(98)23011-8].