Effect of thermal stress on non-collinear antiferromagnetic phase transitions in antiperovskite Mn3GaN compounds with Mn3SbN inclusions

In the designed (1-x)Mn3GaN-xMn3SbN (0.2 < x < 0.8) heterogeneous system, modulating the non-collinear antiferromagnetic (AFM) phase transitions of antiperovskite Mn3GaN using thermal stress is realized for the first time. With growing the Mn3SbN secondary phase, the Neel temperature (TN) of Mn3GaN phase shifts down by 40 K and then disappears, but another magnetic transition below TN appears and shifts up by 125 K. The neutron powder diffraction (NPD) results of the sample with x = 0.6 show that the magnetic transition below TN ascribed to the decreasing Mn-Mn distance (dMn-Mn) and spin re-orientation from Gamma 5g to a new non-collinear M2 AFM phase. By the NPD analysis, the dMn-Mn of the Mn3GaN phase decreases from 2.75527(4) angstrom to 2.73925(3) angstrom, and the angles of the spin rotations for Mn1/Mn2, Mn3-1, and Mn3-2 atoms in M2 AFM during the spin reorientation process are 90 degrees, 60 degrees, and 60 degrees, respectively. Negative thermal expansion behaviors and caloric effects associated with Gamma 5g phase transitions are investigated systematically. Further, the thermal stress could be regulated by adjusting the proportion of Mn3GaN and Mn3SbN phases with mismatched thermal expansion, which could be estimated even up to GPa according to Clausius-Clapeyron relation.

Automated summary

This study demonstrates for the first time the modulation of non-collinear antiferromagnetic phase transition in a heterogeneous system using thermal stress. The addition of a secondary phase leads to a shift in the transition temperature and the appearance of a new magnetic transition. Neutron powder diffraction analysis reveals structural changes and spin reorientation as the cause of the transition.