Effects of Fe doping on structure, negative thermal expansion, and magnetic properties of antiperovskite Mn 3 GaN compounds

We synthesized antiperovskite Mn 3 Ga 1− x Fe x N (0 ≤ x ≤ 0.30) compounds and investigated their negative thermal expansion (NTE) behavior, structure, and magnetic properties. A high‐resolution transmission electron microscopy analysis and a selected‐area electron diffraction (SAED) pattern indicate that the samples have high crystallinity with a single‐phase cubic structure. Tunable NTE behavior appears below room temperature, and the NTE operation temperature range (△ T ) is broadened while increasing the Fe doping. Furthermore, introducing Fe in Mn 3 Ga 1− x Fe x N can efficiently adjust the NTE coefficient from −232.57 × 10 −6 /K ( x = 0) to −12.57 × 10 −6 /K ( x = 0.20), and the corresponding △ T can be broadened from △ T = 22 K to 51 K. Besides, the total entropy change (Δ S total ) at the phase transitions continuously decreases from 9.2 to 4.7 J/(kg K) while increasing the Fe content from x = 0.05 to 0.10. With increasing Fe into Ga sites, the magnetic ordering varies from antiferromagnetic (AFM) to ferromagnetic (FM), the AFM to paramagnetic (PM) phase transition temperature decreases, whereas the FM to PM transition temperature increases when increasing the Fe content. The present study indicates that magnetic element doping can efficiently tune the NTE and the correlated physical features of the antiperovskite compounds.