The structural, electronic, and magnetic properties of (formula presented) (formula presented) Ge, Sn) Heusler compounds have been determined by means of all-electron full-potential linearized augmented plane wave (FLAPW) calculations. We focus on the effects on the electronic and magnetic properties induced by: (i) substitution of the X atom, (ii) applied pressure, and (iii) the use of the local spin density approximation (LSDA) vs the generalized gradient approximation (GGA) in density functional theory. A comparison between LSDA and GGA for the exchange-correlation functional shows that GGA is essential for an accurate description of the equilibrium volumes and of the electronic and magnetic properties of these systems. We find that both the energy gap and the spin gap increase as the X atomic number decreases. As a result of the semiconducting (metallic) character found in the minority (majority) spin band structure, the Si and Ge based alloys are predicted to be half-metallic. In contrast, (formula presented) is found to be a “nearly half-metallic” compound, since the minority valence band maximum crosses the Fermi level. The calculated total magnetization of (formula presented) is in excellent agreement with recent experiments. By including a fully self-consistent treatment of spin-orbit coupling, the GGA calculated orbital moments are shown to be very small (about (formula presented) for Mn and about (formula presented) for Co), showing that the quenching of the orbital magnetic moment is nearly complete. The calculated hyperfine fields, both at zero and elevated pressure, are compared with available experimental data, and show general agreement, except for Mn. Finally, the calculated Mn (formula presented) exchange splittings, found to be in good agreement with experiment, are proportional to the Mn magnetic moments, suggesting a localized nature of ferromagnetism in these Heusler compounds.
|Number of pages||9|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jan 1 2002|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics