Magnetostatic critical point phenomena of ErIGaGARNET

Summary form only given, as follows. The magnetostatic critical point phenomena of a ErIGaGarnet (Er3,(Fe0.2, ,Ga0.8)5 O12) single crystal sphere was investigated by a computer controlled vibrating sample magnetometer (VSM) with a sample heating unit in the uniformly applied bipolar fields from 0 to ±8kOe. The kink point locus was observed for the whole critical region by the extremely low field magnetization measurements. Subtracting the induced large spin paramagnetic moment of Er from the measured values, the Fe sublattice magnetization was successfully separated from the measured value. The critical temperature, the spontaneous magnetization and the zero-field susceptibility were determined without data extrapolation except a few data point measured at very low field foilowing the Miyanati's method applied to YIG. The critical temperature T_c, and the critical indices were obtained to be: T_c = 457.3K, β = 0.433, γ = 1.31, and δ = 4.20. These values do not necessarily agree with the theoretically predicted values. The plot of the equation of states Ψ(H,M) is found to have the same form as those of Ni and Fe which are also investigated by present authors. This result strongly suggests the existence of the universal equation of state Ψ(H,M) for the second-order phase transition.