Mn-based antiperovskite functional materials: Review of research

Our recent research on the Mn-based antiperovskite functional materials AXMn₃ (A: metal or semiconducting elements; X: C or N) is outlined. Antiperovskite carbides (e.g., AlCMn₃) show large magnetocaloric effect comparable to those of typical magnetic refrigerant materials. Enhanced giant magnetoresistance up to 70% at 50 kOe (1 Oe = 79.5775 A·m^-1) over a wide temperature span was obtained in Ga_1-xZn_xCMn₃ and GaCMn_3-xNi_x. In Cu_0.3Sn_0.5NMn_3.2, negative thermal expansion (NTE) was achieved in a wide temperature region covering room temperature (α = -6.8 ppm/K, 150 K-400 K). Neutron pair distribution function analysis suggests the Cu/Sn-Mn bond fluctuation is the driving force for the NTE in Cu_1-xSn_xNMn₃. In CuN_1-xC_xMn₃ and CuNMn_3-yCo_y, the temperature coefficient of resistivity (TCR) decreases monotonically from positive to negative as Co or C content increases. TCR is extremely low when the composition approaches the critical points. For example, TCR is ~ 1.29 ppm/K between 240 K and 320 K in CuN_0.95C_0.05Mn₃, which is one twentieth of that in the typical low-TCR materials (~ 25 ppm/K). By studying the critical scaling behavior and X deficiency effect, some clues of localized-electron magnetism have been found against the background of electronic itinerant magnetism.