Magnetic properties and temperature-dependent half-metallicity of Co2Mn(Ga(1-x)Z(x)) (Z = Si, Ge, Sn) from first-principles calculation

QC 20130422
Using the first-principles exact muffin-tin orbitals method in combination with the coherent potential approximation, we investigated the magnetic properties, exchange interactions, and temperature-dependent half-metallicity of the Co2Mn(Ga(1-x)Z(x)) (Z = Si, Ge, Sn) alloys. The total magnetic moment follows perfectly a previously proposed Slater-Pauling relation, i.e., mu(0) = N-t - 24, with N-t being the number of valence electrons. The Co-Mn and Co1-Co2 (inter-sublattice) interactions are dominated by direct exchange, whereas the Co1-Co1 (intra-sublattice) interaction is characterized by superexchange. The Mn-Mn exchange interaction in Co2MnGa is of long-ranged RKKY-type. However, the Mn-Mn exchange interactions in Co(2)MnZ are relatively localized and can be attributed to superexchange. The Co-Mn, Co1-Co2 and Co1-Co1 total exchange interactions increase with x, whereas the Mn-Mn total exchange interactions show convex behavior. The calculated Curie temperature (T-C) increases with x. The ability of Z to enhance T-C follows the sequence of Si > Ge > Sn, in agreement with the experimental findings. The temperature dependence of the spin polarization at the Fermi level [P(T)] is investigated based on the disordered local moment model. P(T) drops abruptly at temperatures much lower than T-C. At temperatures higher than 200 K, the composition with higher TC generally corresponds to larger P(T).

Hu, Qing-Miao (author)
Li, Chun-Mei (author)
Johansson, BörjeUppsala universitet,KTH,Tillämpad materialfysik,Materialteori(Swepub:uu)borjejs (author)
Vitos, LeventeUppsala universitet,KTH,Tillämpad materialfysik,Materialteori(Swepub:uu)lvi21721 (author)
Yang, Rui (author)
KTHTillämpad materialfysik (creator_code:org_t)

By the author/editor: Luo, Hu-Bin; Hu, Qing-Miao; Li, Chun-Mei; Johansson, Börje; Vitos, Levente; Yang, Rui

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