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

Abstract

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 Γ5g to a new non-collinear M2 AFM phase. By the NPD analysis, the dMn–Mn of the Mn3GaN phase decreases from 2.75527(4) Å to 2.73925(3) Å, and the angles of the spin rotations for Mn1/Mn2, Mn3-1, and Mn3-2 atoms in M2 AFM during the spin re-orientation process are 90°, 60°, and 60°, respectively. Negative thermal expansion behaviors and caloric effects associated with Γ5g 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.