Atomic diffusion in Ni-Mn mechanical alloys around Ni3Mn composition proved from magnetic measurements

The character of thermal diffusion of magnetic atoms has been investigated in Ni-Mn mechanical alloys around Ni3Mn composition by monitoring magnetic properties during the atomic ordering process. Observed susceptibility versus temperature curve after annealed at the ordering temperature of 693 K for 50 h shows at least four steps. Those multi steps came into two at the final stage of annealing for 1000 h. The step at the highest temperature corresponds to the Curie temperature TC of Ni3Mn. The observed variation of TC with annealed time was explained by solving a diffusion equation, and the range of the concentration fluctuation was determined to be 4 nm.