Unusual Electrical Transport Driven by the Competition between Antiferromagnetism and Ferromagnetism in Antiperovskite Mn₃Zn1-xCoxN.

The magnetic, electrical transport and thermal expansion properties of Mn₃Zn1-xCoxN (x = 0.2, 0.4, 0.5, 0.7, 0.9) have been systematically investigated. Co-doping in Mn₃ZnN complicates the magnetic interactions, leading to a competition between antiferromagnetism and ferromagnetism. Abrupt resistivity jump phenomenon and negative thermal expansion behavior, both associated with the complex magnetic transition, are revealed in all studied cases. Furthermore, semiconductor-like transport behavior is found in sample x = 0.7, distinct from the metallic behavior in other samples. Below 50 K, resistivity minimum is observed in samples x = 0.4, 0.7, and 0.9, mainly caused by e-e scattering mechanism. We finally discussed the strong correlation among unusual electrical transport, negative thermal expansion and magnetic transition in Mn₃Zn1-xCoxN, which allows us to conclude that the observed unusual electrical transport properties are attributed to the shift of the Fermi energy surface entailed by the abrupt lattice contraction.