Noncoplanar antiferromagnetism induced zero thermal expansion behavior in the antiperovskite Mn3Sn0.5Zn0.5Cx

Zero thermal expansion (ZTE) is one of the most fascinating phenomena in condensed-matter physics due to its strong correlation essence and great application prospect. However, the origin of ZTE remains elusive and it becomes an overwhelming challenge to realize the controllable design for which magnetic interaction plays a key role. In this work, with the help of neutron powder diffraction analysis, a noncoplanar [21, 12, 12 ] antiferromagnetic (AFM) phase is experimentally obtained in the antiperovskite system Mn3Sn0.5Zn0.5Cx. It shows ZTE behavior in a particularly wide temperature range from 10 to 162 K with linear thermal expansion coefficient 9.3 x 10-7 K-1. Herein, the theoretical spin model is combined with the experimental results to well understand the strong spin-lattice correlation between AFM ordering and ZTE behavior. The ZTE in the noncoplanar antiferromagnetic ordered system is attributed to the fierce competition between the nearest AFM direct exchange and ferromagnetic superexchange interaction, which is effectively tuned by C occupation. Our work not only paves the way toward understanding the physical origin of ZTE, but it also provides a feasible strategy for the ZTE design, which is also of great significance for promoting the study of a strong correlation system.