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要旨:
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.
