Conversion of magnetic structure by slight dopants in geometrically frustrated antiperovskite Mn3GaN

We found that a few percent of Fe dopants at the Mn sites alters the antiferromagnetic spin structure of Mn3GaN and induces a first-order antiferromagnetic-ferromagnetic phase transition accompanied by a large volume change. The drastic conversion of the spin alignment originates from phase competition due to a geometrical frustration in the Mn6N octahedron. This result demonstrates that the magnetic and other unique related properties of manganese antiperovskites are controllable by element substitution. Comparing with the ferromagnetic state in Mn3Ga(N1−xCx), we discuss a possible spin structure that accounts for the conversion of the magnetic states.