Study of the structural and magnetic properties and gallium exchange phenomenon in a Mn-Ga alloy doped by Cr during the milling and annealing process

The effect of milling and annealing process on Cr doped Mn3Ga nanocrystallite has been investigated. Phase determination analysis shows that Ga turning to get out of Mn-Ga structure and tend to make bonding to Cr and form Cr3Ga4 product during milling process. Annealing of the new phases lead to decomposition of Cr3Ga4 and formation of a new Mn-Ga phase in reverse direction, in the other words diffusion of Ga atoms occurs from Cr3Ga4 to Mn phase and α-Mn and Cr3Ga4 change to Mn3Ga2 and Cr phases. The variation of coersivity, magnetization and magnetic state of different samples was explained according to the crystallite size of the present phases and grain boundary effects. It was also confirmed that formation of Mn-Cr clusters plays an important role in increase of saturation magnetization.