Transition from antiferromagnetic ground state to robust ferrimagnetic order with Curie temperatures above 420 K in...

Manganese (Mn)-based antiperovskite structures (Mn₃AX, where A and X represent the 3d transition-metal elements and N or C atoms, respectively) have attracted growing attention because of their novel electronic and magnetic properties. However, the lack of an effective approach to regulate the magnetic coupling in Mn₃AX crystal structure, particularly in antiferromagnetic ground states, hinders their further design and applications. Herein, robust high-temperature ferrimagnetic order with a Curie temperature ( $T_C$ ) in the range of ~390-420 K was successfully achieved in $M{n}_{3}G{a}_x{N}_x$ ( $x=0.5$ , 0.6, and 0.7) via composition-deficient engineering. A systematic investigation, including synchrotron X-ray diffraction, neutron powder diffraction, pair distribution function, X-ray absorption near-edge structure, magnetic characterization, and first-principles calculations, convincingly indicated that the redistribution of partial atoms in the antiferromagnetic ground state was responsible for the observed long-range magnetic order. These results not only provide a new perspective into the design and construction of high-temperature ferrimagnets based on the Mn₃AX structure, but also open up a promising avenue for the further design of Mn₃AX-based spintronic or other multifunctional devices.