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Using first principles calculations based on density functional theory, we study electronic and magnetic properties of CoIrMnZ (Z = Al, Si, Ga, Ge) Heusler systems. Based on the electronic structure calculations, CoIrMnSi and CoIrMnGe are predicted to be half-metallic. For the studied systems, the ground state magnetic configurations are found to be ferromagnetic with magnetic moment consistent with the Slater-Pauling rule. The calculated ferromagnetic transition temperatures are much higher than the room temperature for all the cases. The effect of spin orbit coupling has been discussed on the electronic structure for all the systems studied here. Furthermore, we construct junctions with MgO along (001) direction. The MnZ terminations are found to be energetically more favourable compared to the CoIr terminations. After discussing the tunnelling conductance, we find that CoIrMnSi/MgO/CoIrMnSi could be a promising magnetic tunnelling junction (MTJ) candidate.

金沢大学大学院自然科学研究科計算科学, 金沢大学理学部, We have developed a fully relativistic pseudopotential in the planewave method. The pseudopotential shows the sufficient transferability that the error is much smaller than the energy splitting of spin-orbit coupling. This pseudopotential scheme has been implemented for bulk systems, surfaces, and the thin magnetic film on the metal. © 2006 Elsevier B.V. All rights reserved.