Giant Negative Thermal Expansion in Antiferromagnetic CrAs -Based Compounds

CrAs is a well-known superconductor, which shows a pronounced volume contraction around a Néel temperature (TN) of 260 K. However, it has not been considered as a negative thermal expansion (NTE) material for industrial applications partially because the temperature window of its phase transition is limited and does not cover room temperature. We prepare some CrAs-based compounds (Cr0.98Ni0.02As, CrAs, and CrAs0.91S0.09) and investigate their linear NTE properties. By chemical modification, a giant NTE can be realized in this system with a broad temperature window of 218 K from 122 to 340 K. Typically, a linear NTE coefficient of -28.3×10-6K-1 in a broad NTE operation-temperature window of 98 K (from 242 to 340 K) is obtained in the CrAs0.91S0.09 compound. In the region between 275 and 315 K around room temperature, the linear NTE coefficient (-51.2×10-6K-1) remains nearly independent of temperature. In addition, the CrAs-based compounds show large thermal and electrical conductivities and their dimensions are insensitive to the external magnetic field. The aforementioned excellent properties suggest that the CrAs-based compounds can serve as an alternative type of NTE materials and have promising applications, especially in the magnetic field environment.