Electronic structure of metallic antiperovskite compound GaCMn₃

We have investigated the electronic structures of antiperovskite GaCMn₃ and related Mn compounds SnCMn₃, ZnCMn₃, and ZnNMn₃. In the paramagnetic state of GaCMn₃, the Fermi surface nesting feature along the ΓR direction is observed, which induces the antiferromagnetic (AFM) spin ordering with the nesting vector Q∼ΓR. Calculated susceptibilities confirm the nesting scenario for GaCMn₃, and also explain various magnetic structures of other antiperovskite compounds. Through the band folding effect, the AFM phase of GaCMn₃ is stabilized. Nearly equal densities of states at the Fermi level in the ferromagnetic and AFM phases of GaCMn₃ indicate that two phases are competing in the ground state.