Pressure-induced new spin-states in Ni-25at%Mn mechanical alloy under high pressure

AC-susceptibility measurements in mechanically alloyed Ni-25at%Mn were made under high hydrostatic pressures up to 7.5 GPa by using a cubic anvil press in the low-temperature range from 4.2 K to 300 K. At ambient pressure a reentrant spin glass (RSG) state was observed below 58 K, followed by a ferromagnetic (FM) state with the Curie temperature (T-C) at 120 K. T-C decreased with increasing pressure up to 4.3 GPa, while the transition temperature from RSG to FM increased to merge with T-C at 70 K, and then, with further increasing pressure the FM state disappeared, and a spin glass (SG) state appeared. The local moments of this high-pressure SG phase decreased with pressure. The results were compared with a bulk alloy made by the conventional method of melting. In the bulk alloy, a new high-pressure magnetic phase appeared having almost pressure-independent local magnetic moments.