Electronic and magnetic structures of CuAu-type MnNi and MnGa have been studied by LMTO-ASA including the spin-orbit interaction in the frame of the LSD. In MnNi, the anti-parallel arrangement of the Mn moments lowers the electronic energy by forming a pseudo-gap in the energy bands. The Mn moment lies in the c-plane with a value of 3.29 μB. The magnetocrystalline anisotropy constant, Ku is found to be -9.7 × 105 J/m3. In MnGa, the hybridization between the Mn d electrons and the delocalized Ga p electrons promotes an itineracy of the Mn d electrons. This reduces the Mn moment to 2.51 μB but aligns the moments ferromagnetically along the c-axis with Ku of 2.6 × 106 J/m3. Based on these two results, we have discussed the condition of metallic ferromagnetism of the Mn alloys.
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