Exchange interactions, spin waves, and transition temperatures in itinerant magnets

• Published in: Philosophical magazine (Abingdon, England) England), 2006-04, Vol.86 (12), p.1713-1752
• Main Authors: Turek, I., Kudrnovský, J., Drchal, V., Bruno, P.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; General theory and models of magnetic ordering; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Physics; Spin waves
• ISSN: 1478-6435; 1478-6443; 1478-6433
• DOI: 10.1080/14786430500504048

This contribution reviews an ab initio two-step procedure to determine exchange interactions, spin-wave spectra, and thermodynamic properties of itinerant magnets. In the first step, the self-consistent electronic structure of a system is calculated for a collinear spin structure at zero temperature. In the second step, parameters of an effective classical Heisenberg Hamiltonian are determined using the magnetic force theorem and the one-electron Green functions. The Heisenberg Hamiltonian and methods of statistical physics are employed in subsequent evaluation of magnon dispersion laws, spin-wave stiffness constants, and Curie/Néel temperatures. The applicability of the developed scheme is illustrated by selected properties of various systems such as transition and rare-earth metals, disordered alloys including diluted magnetic semiconductors, ultrathin films, and surfaces. A comparison to other ab initio approaches is presented as well.