Antisite disorder and phase segregation in Mn₂NiSn

Abstract

A systematic study of crystal structure, local structure, magnetic and transport properties in quenched and temper annealed Ni2−xMn1+xSn alloys indicate the formation of Mn3Sn type structural defects caused by an antisite disorder between Mn and Sn occupying the Y and Z sublattices of X2YZ Heusler structure. The antisite disorder is caused by the substitution of Ni by Mn at the X sites. On temper annealing, these defects segregate and phase separate into L21 Heusler and D019 Mn3Sn type phases.

Defect induced ferromagnetism in Mn3Ga

“…Phase separation due to temper annealing has been reported in several families of Mn-rich Heusler alloys like Ni 2 Mn 1+x Z 1−x , Mn 2 NiZ (Z = Ga, In, Sn or Sb) [19,20,34,41,43]. The present study shows that even Ni-substituted Mn 3 Ga is prone to phase separation.…”

“…Segregation of structural defects is known to induce phase separation upon temper annealing. Such phase separation is observed in several families of Mn-rich alloys like Ni 2 Mn 2−x Z x [20], Mn 2 NiSn [34] and Mn 2 NiGa [41]. Therefore, it will be worthwhile to investigate the effect of temper annealing on Mn 2.75 Ni 0.25 Ga. Mn 3 Ga is known to undergo a structural transformation from a disordered cubic phase to a tetragonal D0 22 phase on annealing at about 400 • C [23].…”

“…Will there be any inhomogeneous magnetic properties in such compounds due to AF-FM interactions? Further, Mn-rich Heusler alloys are shown to be metastable against temper annealing due to the segregation of defect phases [34,35]. It would also be interesting also to study the stability of Ni-substituted Mn 3 Ga.…”