Transformation—Disorder to Order in Ni3Mn

Abstract

The ordering transformation in the alloy Ni₃Mn has been investigated using both magnetic and neutron diffraction techniques. These measurements were made with alloys that were allowed to relax to nearly equilibrium states of order over a range of temperatures above and below the critical ordering temperature. In addition, the manner in which these equilibrium states were approached isothermally was also investigated over a range of temperatures. From these measurements, it has been postulated that the equilibrium configurations of partial order are nonhomogeneous, consisting of long‐range ordered domains in a matrix of short‐range order. In addition, the isothermal transformation from disorder to long‐range order proceeds first by the development of short‐range order. Both short‐ and long‐range order have been found to increase the magnetic Curie temperature as well as the magnetization above that of the weakly magnetic disordered alloy. These results support the hypothesis that nearest neighbor magnetic‐spin interactions play an important role in determining these magnetic properties, although the importance of more distant neighbor interactions cannot be ruled out.