Electronic structure of metallic antiperovskite compound ${\mathrm{GaCMn}}_3$

We have investigated the electronic structures of antiperovskite ${\mathrm{GaCMn}}_3$ and related Mn compounds ${\mathrm{SnCMn}}_3,$ ${\mathrm{ZnCMn}}_3,$ and ${\mathrm{ZnNMn}}_3.$ In the paramagnetic state of ${\mathrm{GaCMn}}_3,$ the Fermi surface nesting feature along the $\Gamma R$ direction is observed, which induces the antiferromagnetic (AFM) spin ordering with the nesting vector $\mathbf{Q}\sim \Gamma R.\mathrm{}$ Calculated susceptibilities confirm the nesting scenario for ${\mathrm{GaCMn}}_3,$ and also explain various magnetic structures of other antiperovskite compounds. Through the band folding effect, the AFM phase of ${\mathrm{GaCMn}}_3$ is stabilized. Nearly equal densities of states at the Fermi level in the ferromagnetic and AFM phases of ${\mathrm{GaCMn}}_3$ indicate that two phases are competing in the ground state.