Exotic magnetic interactions in solids: first-principle modeling

Abstract: The magnetic materials might be sub-divided into the three major classes that requires special approaches and has specific problems, but also allowing for specific simplifications. This classes are magnetic insulators, 4f-metals with high degree of the magnetic moment localizations and d-metals and intermetallic compounds and alloys. For the first classes an important role of the correlation effects are evident, but quantum Heisenberg model with some modifications provide robust description of the finite temperature magnetic properties. The class of the d-metallic systems is less correlated but the construction of the proper magnetic model is difficult since the spin moments fluctuates also in their magnitude. The 4f-metals are intermediate case where localized correlated shells coexist with non-correlated conduction band that mediates inter-site interactions. In the talk I will illustrate how one can deal with specific problems of these classes of materials using as examples oxides with complex magnetic order ( e.g. Sr₂RuO₄, UO₂), canonical 4f and 3d ferromagnetic metals (hcp Gd, bcc Fe and fcc Ni), some functional magnetic alloys , and intermediate hybrid case of DyCo₅. The novel approach for ab-initio based modelling of the longitudinal spin-fluctuations in metals and examples of the magnetic multistate simulations will be presented. The examples of the systems where the effects of exotic interactions of relativistic (pseudodipolar and multipolar) and isotropic multi-site (4-sites ring, bi-quadratic) origin plays an important role will be given.