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Abstract

In this paper, results of ab initio band structure calculations for A(2)BC Heusler compounds that have A and B sites occupied by transition metals and C by a main group element are presented. This class of materials includes some interesting half-metallic and ferromagnetic properties. The calculations have been performed in order to understand the properties of the minority band gap, the peculiar transport properties and magnetic behaviour found in these materials. Among the interesting aspects of the electronic structure of the materials are the contributions from both A and B atoms to the total magnetic moment. The magnitude of the total magnetic moment shows a trend consistent with the Slater - Pauling type behaviour in several classes of these compounds. The total magnetic moment also depends on the kind of C atoms although they do not directly contribute to it. In Co-2 compounds, a change of the C element changes the contribution of the t(2g) states to the moment at the Co sites. The localized moment in these magnetic compounds resides at the B site. Other than in the classical Cu-2-based Heusler compounds, the A atoms in Co-2, Fe-2 and Mn-2-based compounds may contribute significantly to the total magnetic moment. It is shown that the inclusion of electron - electron correlation in the form of LDA + U calculations helps to understand the magnetic properties of those compounds that already exhibit a minority gap in calculations where it is neglected. Besides the large group of Co-2 compounds, half-metallic ferromagnetism was here found only in such compounds that contain Mn.