Electrical and magnetic properties, and electronic structures of pseudo-gap-type antiferromagnetic L1₀-type MnPt alloys

The electrical resistivity ρ, magnetic susceptibility χ, electronic specific heat coefficient γ_e, the Néel temperature T_N and the electronic structure and the magnetocrystalline anisotropy energy (MAE) have been investigated for L1₀-type MnPt alloy system. This alloy system exhibits the characteristic behaviors of pseudo-gap type antiferromagnets, presenting with the highest T_N, the smallest values of ρ, χ and γ_e in the vicinity of the equiatomic composition. The values of ρ, χ and γ_e increase with deviating from the equiatomic composition. From the linear muffin-tin orbital (LMTO) band calculations, the L1₀-type MnPt alloy system has a pseudo-gap in the electronic structure and the density of states (DOS) at the Fermi energy (E_F) is lowest at the equiatomic composition in accord with the experimental results. Furthermore, the results of the LMTO band calculations including the spin-orbit interaction make it clear that the direction of the magnetic moment of Mn in the equiatomic composition is parallel to the c-axis, consistent with the reported spin structure determined by neutron diffractions. The magnetocrystalline anisotropy constant K is about 1.39 × 10⁶ J m^-3 which is larger in magnitude than that of L1₀-type MnNi equiatomic alloy, though the signs are different.