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

Abstract

We report the discovery of a large negative thermal expansion (NTE) up to $\alpha =-25\times {10}^{-6}{\mathrm{K}}^{-1}$ ($\alpha$ : coefficient of linear thermal expansion) in Ge-doped anti-perovskite manganese nitrides ${\mathrm{Mn}}_{3}A\mathrm{N}$ $(A=\mathrm{Cu},\mathrm{Zn},\mathrm{Ga})$ . This gigantic NTE is several to ten times higher than that of commercially available NTE materials. The discontinuous lattice expansion seen in pure ${\mathrm{Mn}}_{3}A\mathrm{N}$ is broadened by Ge substitution over a wide temperature window, at widest $\Delta T\sim 100\mathrm{K}$ , around room temperature. Such a large, isotropic and nonhysteretic NTE is desirable for practical applications.