Magnetovolume effect and negative thermal expansion in Mn 3(Cu1-xGex)N

Abstract

Metallic manganese nitrides Mn3AN (A = Zn, Ga, etc) are well-known for their large magnetovolume effect (MVE), i.e., a discontinuous volume expansion at the magnetic transition. However, MVE is exceptionally absent in Mn3CuN. We found that MVE is recovered by a small amount of Ge in the Cu site. This revival seems to coincide with recovery of the cubic structure. By further Ge doping, the volume expansion becomes gradual (ΔT ∼ 100 K) and large negative thermal expansion (NTE) is exhibited around room temperature [α = -12 × 10-6 K-1 (α: coefficient of linear thermal expansion) for Mn3(Cu 0.5Ge0.5)N]. Such a large, isotropic and non-hysteretic NTE is desirable for practical applications. © 2006 The Japan Institute of Metals.