Linear and non-linear scaling in speromagnetic systems

The authors report AC susceptibility and magnetization studies on glasses with composition Gd/sub 65-x/Tb/sub x/Co35 for 0 < x < 65. With increasing x random magnetic anisotropy (RMA) is introduced in a controlled fashion. The effect of increasing x is to replace the ferrimagnetic (FM) transition of Gd65Co35 with a speromagnetic (SM) one. The linear (M) and non-linear (M = X10 H-M) magnetization were studied in the Tb x = 50 alloy. They find that the magnetization isotherms follow a non-linear scaling for H < 1 kOe much like that found in spin-glass systems where exchange fluctuations are strong. For H > 1kOe the magnetization crosses over to standard linear critical behavior expected for a FM transition. These results show that a FM-like state may be induced in an RMA system for large enough applied fields. They will discuss these results in terms of the strong RMA and strong ferromagnetic exchange present in these systems