Ni-Mn-Sn Heusler: milling and annealing effect on structural and magnetic properties

Nanocrystalline Ni₅₁Mn₁₉Sn₃₀ Heusler alloy was prepared in the form of powder by solid state reaction in a planetary ball mill under argon atmosphere. After 10 h of milling the samples exhibit a mixture of two phases: disordered Heusler structure and half-Heusler structure. The stability of the phases was studied and a transformation of the disordered Heusler phase into the ordered Heusler and Ni₃Sn₂ phase was observed after heat treatment. Magnetic properties strongly depend on the phases promoted during milling and annealing. The phase change after annealing leads to the increase of the sample's magnetisation. (paper)