Influence of carbon concentration on structural, magnetic and electrical transport properties for antiperovskite compounds AlCxMn3

The structural, magnetic and transport properties of the antiperovskite AlCxMn3 (1.0≤x≤1.4) are investigated. It is found that the lattice parameter a increases monotonously with nominal carbon concentration x. The Curie temperature TC increases with increasing x from 1.0 to 1.1 and then decreases with further increasing x. The highest TC value is 364 K, about 70 K higher than that of stoichiometric AlCMn3 reported previously. This may be attributed to a competition between the lattice expansion and the strong Mn 3d-C 2p hybridization. Below 100 K, the resistivity can be well described as ρ(T)=ρ0+AT2, corresponding to the electron-electron scattering. A increases with x, suggesting certain changes in the electronic structure, e.g. carrier density. Above 250 K, all ρ(T) curves depart from the linear dependence on temperature and seem to take on a tendency towards saturation.