Hydrostatic Pressure Dependence of Forced Volume Magnetostriction of Seven Amorphous Alloys

Forced volume magnetostriction is too minute 10-10~10-9[(103/4)(A/m)]-1 to be measured accurately by repeated addition of linear magnetostriction 10-6[(103/4)(A/m)]-1. According to thermodynamic relation, (d/dH)T,p=-(dMs/dp)T,H ,we measured the Ms-p curve and obtained the hydrostatic pressure dependence of forced volume magnetostriction of seven amorphous alloys－Fe81.6Si4.6B13.8, Fe46.3Co0.03Ni46.5Si3.75V0.92B2.5, Fe75Cr5Si5B15, Fe73.9Co8.3Si4.4B13.4, Fe75Ni5Si5B15, Fe78.75Cu1.25Si5B15 and (Fe0.85Co0.15)82Cu0.4Si4.4B13.2 in the range from 0.000 1 to 2.4 GPa. The results show clearly two kinds. (1) Six of them belong to the first type of pressure effect on magnetism. (d/dH)T,p is positive under most of pressure, i. e. Ms diminishes when p increases. (d/dH)T,p is negative only in some narrow ranges of pressure. It is due to variation of chemical short range order which is composed of magnetic atoms and non-magnetic atoms under different pressure. (2) Amorphous alloy Fe78.75Cu1.25Si5B15 belongs to the second type of pressure effect on magnetism. (d/dH)T,p is negative under most of pressure. Anomalous rise of Ms is related to the special role of Cu.