Magnetism in layered materials

Sammanfattning: Magnetic properties of layered materials have been studied by means of electronic structure calculations based on density functional theory.The occurrence of confined quantum-well states in thin films has been investigated and put into relation with the topology of the corresponding bulk Fermi surface. The quantum-well states are shown to give rise to small shifts of the magnetization in thin films embedded in a magnetic host material. Under certain circumstances this effect is found to induce magnetism in layered systems composed of materials which are nonmagnetic in bulk.The oscillatory magnetic interlayer coupling is investigated and connected to details of the electronic structure of the constituent materials. In addition, it is shown how interface roughness may influence the coupling.A long ranged oscillatory interaction between localized interface states is found and explained in terms of quantum interference.The interface magnetism of several 3d transition metals is calculated and the sometimes enhanced or reduced interface magnetization is explained in terms of the magnetic behavior of the corresponding bulk alloys.A superposition principle is proposed which makes it possible to determine the magnetic profile of a variety of layered systems, starting from a limited number of independent magnetization profiles of bilayer interfaces.The magnetic anisotropic energy of thin Ni films deposited on Cu is calculated and it is shown how the different contributions from the surface/interface, lattice distortion and quantum size effects can be separated.Spin density waves in chromium films embedded in different host materials have been calculated and analyzed.In order to analyze interface stabilities, an interface mixing energy is introduced and a rule of thumb estimate of the stability is proposed, involving a simple scaling relation between the bulk and interface mixing energy.Finally, an efficient supercell Green's function method with a computational cost scaling linearly with the number of atoms has been developed.