MAGNETIZATION PROCESS OF THE MIXED COMPOUND WITH EXCHANGE FRUSTRATIONS FE0.65MN0.35TIO3 AND FE0.50MN0.50TIO3-ANOMALOUS DEPENDENCE ON THE SWEEP-RATE OF MAGNETIC-FIELDS

The magnetization processes of the spin-glass Fe0.50Mn0.50TiO3 and the reentrant spin-glass Fe0.65Mn0.35TiO3 have been measured in the magne tic field H swept with various sweep-rates between 0.050 T/s and 0.750 T/s at 4.2 K and similar to 1.4 K. When H is swept up or down fast be yond a critical value of the sweep-rate, the anomalous jump-up and jum p-down of the magnetization occurs towards the values of the field-coo led-magnetization. The jump-up or jump-down field of the magnetization changes depending on the sweep-rate and the temperature. It is demons trated that the hysteresis related to the jump of the magnetization be comes small gradually with increasing the sweep-rate, which is opposit e to the normal behavior that the response of spin systems is delayed for a fast sweep of H. We consider that these phenomena are closely re lated to the properties of the spin-glass state.