The modern version of the KKR (Korringa–Kohn–Rostoker) method represents the electronic structure of a system directly and efficiently in terms of its single-particle Green's function (GF). This is in contrast to its original version and many other traditional wave-function-based all-electron band structure methods dealing with periodically ordered solids. Direct access to the GF results in several appealing features. In addition, a wide applicability of the method is achieved by employing multiple scattering theory. The basic ideas behind the resulting KKR-GF method are outlined and the different techniques to deal with the underlying multiple scattering problem are reviewed. Furthermore, various applications of the KKR-GF method are reviewed in some detail to demonstrate the remarkable flexibility of the approach. Special attention is devoted to the numerous developments of the KKR-GF method, that have been contributed in recent years by a number of work groups, in particular in the following fields: embedding schemes for atoms, clusters and surfaces, magnetic response functions and anisotropy, electronic and spin-dependent transport, dynamical mean field theory, various kinds of spectroscopies, as well as first-principles determination of model parameters.

https://iopscience.iop.org/article/10.1088/0034-4885/74/9/096501/pdf

Calculating condensed matter properties using the KKR-Green's function method—recent developments and applications

A review is given on the basic properties of 2:14:1 hard magnetic phases as well as technological procedures used for manufacturing R-Fe-B and R-Fe-C permanent magnets. First, we analyse the phase diagrams, crystal structure of hard magnetic phases and composition ranges in which these phases form solid solutions, as a result of various types of substitution. Then, the magnetic properties of and -based compounds are described. The routes used for manufacturing R-Fe-B and R-Fe-C permanent magnets are detailed. The magnets' microstructure as well as their coercivities are described in correlation with composition and manufacturing routes. The properties of nanostructure magnets are then presented. Finally, the stability of Nd-Fe-B and Nd-Fe-C magnets in various working conditions is analysed.

Permanent magnets based on R-Fe-B and R-Fe-C alloys

Theory of hyperfine interactions in metals

Relationship between the magnetic hyperfine field and the magnetic moment

Co alloys with Cr, Fe, Ru and Cu in the low concentration range have been studied by 59Co NMR. Regularly spaced satellite lines are observed that develop with increasing impurity concentration. The satellite intensities as a function of the impurity concentration have been compared with the binomial distribution law of particular Co environments. Deviations from the exact binomial law in some cases are briefly discussed against the properties of their respective phase diagrams. From this comparison it is concluded that satellite frequencies are primarily determined by the number of impurity atoms in the first neighbour shell: each additional impurity atom in the shell introduces a constant (element-dependent) modification to the hyperfine field value on a Co site. This assignment of satellite frequency shifts to given configurations in the first coordination shell provides references for structural investigations in related binary metallic systems such as metallic multilayers. Preliminary results for CoPt alloys are also presented which do not follow the systematics of the previous alloys but rather suggest an extended oscillating perturbation around Pt impurities.

http://iopscience.iop.org/article/10.1088/0953-8984/5/10/012/pdf

Satellite structure of 59Co NMR spectra in some Co alloys

The hyperfine fields in the substitutionally disordered BCC alloy systems FexCr1-x and FexCo1-x have been studied by means of charge self-consistent Korringa-Kohn-Rostoker coherent potential approximation (KKR CPA) electronic structure calculations. For the various components, the contribution to the Fermi contact hyperfine field due to core polarisation was found to be proportional to the corresponding local spin moment. The contributions of the conduction band, however, did not show such a simple behaviour and turned out to be dominated by the occupation of the s bands for spin up and down. To study the influence of relativistic effects on the hyperfine fields the corresponding matrix elements for the Fermi contact interaction have been calculated nonrelativistically as well as fully relativistically. The importance of contributions to the hyperfine fields coming from non-s electrons have been investigated by performing spin-polarised relativistic linear muffin tin orbital method (SPRLMTO) band structure calculations for hypothetically ordered alloys.

F.J. Pinski

Papers

A theoretical study of the hyperfine fields in BCC FexCr1-x and FexCo1-x alloys