Giant negative thermal expansion in Ge-doped anti-perovskite manganese nitrides

We report the discovery of a large negative thermal expansion (NTE) up to alpha=-25x10(-6) K-1 (alpha: coefficient of linear thermal expansion) in Ge-doped anti-perovskite manganese nitrides Mn(3)AN (A=Cu,Zn,Ga). This gigantic NTE is several to ten times higher than that of commercially available NTE materials. The discontinuous lattice expansion seen in pure Mn(3)AN is broadened by Ge substitution over a wide temperature window, at widest Delta T similar to 100 K, around room temperature. Such a large, isotropic and nonhysteretic NTE is desirable for practical applications. (c) 2005 American Institute of Physics.