Negative thermal expansion and magnetic transition in anti-perovskite structured Mn₃Zn_1-xSn_xN compounds

The thermal expansion properties of Mn₃Zn_1-xSn _xN (x=0.1, 0.2, 0.3, 0.5, 0.8, 1.0) compounds were investigated by variable temperature X-ray powder diffraction. With increasing Sn content, the thermal expansion behavior of Mn₃Zn_1-xSn_xN changes from positive to negative and returns to positive near the magnetic transition temperature range. Moreover, the magnetic transition temperature increases from 185 to 495 K. It is interesting that the abnormal thermal expansion behavior of Mn₃Zn_1-xSn_xN is related to the number of valence electrons on Zn site and the equivalent effect with three valence electrons is beneficial for displaying negative thermal expansion. In addition, the antiferromagnetic order state gradually canted with the increasing Sn content due to the increase of Mn-Mn distance.