24.12.2010

Low thermal expansion behavior and electrical conductivity of Mn₃(Cu_0.5Si_xGe_0.5−x)N at low temperatures

Rongjin Huang^a, Zhixiong Wu^a^,^b, Xinxin Chu^a^,^b, Huihui Yang^a^,^b, Zhen Chen^a^,^b and Laifeng Li^a^,^,

^a Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China

^b Graduate University of Chinese Academy of Sciences, Beijing 100080, PR China

Received 17 June 2010;

revised 3 August 2010;

accepted 9 August 2010.

Available online 17 August 2010.

Abstract

Anti-perovskite manganese nitrides with the general formula Mn₃(Cu_0.5Si_xGe_0.5−x)N (x = 0.05, 0.1, 0.15, 0.2) were fabricated by mechanical ball milling followed by solid state sintering. The temperature dependence of thermal expansions, magnetic properties and electrical conductivities were investigated in the temperature range of 77–300 K. The results show that the operation-temperature window of negative thermal expansion (NTE) shifts to lower temperature and the magnitude of NTE becomes smaller with increasing Si content. Very low average coefficients of thermal expansion of 1.3 × 10⁻⁶ K⁻¹ and 1.65 × 10⁻⁶ K⁻¹ were observed in Mn₃(Cu_0.5Si_0.1Ge_0.4)N and Mn₃(Cu_0.5Si_0.15Ge_0.35)N within the temperature range of 77–300 K, respectively. In addition, the electrical conductivities of all the samples are in the range of 2.5–3.5 × 10⁵ (ohm m)⁻¹.

Abstract

Graphical abstract