Giant Negative Thermal Expansion in Antiferromagnetic CrAs-Based Compounds

Materials featuring negative thermal expansion (NTE) attract attention due to their numerous applications in printed circuit boards, machinery, optical-fiber reflective grating devices, and high-precision mirrors. Unfortunately, most large samples of NTE material are very sensitive to external magnetic fields. To address this stumbling block, the authors chemically modify CrAs, which can turn antiferromagnetic and thus field-insensitive, and obtain a large NTE coefficient across a large range that includes room temperature. Electrons in $3d$ orbitals are responsible for NTE, accompanied by a first-order antiferromagnetic-paramagnetic transition.