Negative thermal expansion in Ge-free antiperovskite manganese nitrides: Tin-doping effect

摘要

Giant negative thermal expansion (NTE) recently discovered in antiperovskite manganese nitrides Mn_3AN (A=Zn,Ga, etc.) is achieved by doping Ge on A as "relaxant" of the sharp volume change at the magnetic transition. To promote wider applications, we synthesized NTE antiperovskites without expensive Ge. We discovered that Sn broadens the volume change, though less effective than Ge. Simultaneous substitution of Sn for A and C for N expands the operation-temperature window of NTE almost as broad as that of the Ge-doped counterpart. We discuss relation between the broadening and the phase instability caused by Ge or Sn.