Electronic structure of metallic antiperovskite compound GaCMn$_3$

We have investigated the electronic structures of antiperovskite GaCMn 3 and related Mn compounds SnCMn 3 , ZnCMn 3 , and ZnNMn 3 . In the paramagnetic state of GaCMn 3 , 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 GaCMn 3 , and also explain various magnetic structures of other antiperovskite compounds. Through the band folding effect, the AFM phase of GaCMn 3 is stabilized. Nearly equal densities of states at the Fermi level in the ferromagnetic and AFM phases of GaCMn 3 indicate that two phases are competing in the ground state.