Calculation of magnetism and its crystal structure dependence

Sammanfattning: The subject of the present thesis is a theoretical investigation of magnetism and its crystal structure dependence by means of electronic-structure calculations from first principles. The theoretical treatment is based on density functional theory and the so called linear muffin-tin orbital method is used in its full-potential version as well as in an atomic sphere approximation.A detailed theoretical investigation of the magnetic and structural properties of all the binary alloys between the 3d elements Fe, Co, Ni, and Cu is performed. Alloying effects are treated by a mean field approximation called the coherent potential approximation. Theory is able to reproduce experiments regarding both magnetic and structural properties and gives an understanding of the physics behind the formation of magnetic moments and the correlation between magnetism and structural stabilily.The magnetic anisotropy energy of especially the magnetic 3d elements Fe, Co, and Ni in their cubic ground structures and in tetragonal and trigonal structures are calculated and from this also different magnetostriction coefficients have been studied. The correlation between the orbital moment anisotropy and the total energy anisotropy is studied both by means of numerical experiments and by perturbation theory. Different theoreticalapproaches have been tested and compared.Further, the magnetic anisotropy has been studied for some intermetallic compounds, for which the anisotropy is rather large, such as MnX (X=As, Sb, Bi), VAu4, FePt.Together with experimental physicists and chemists the (Fe1-yXy)3P (X=Mn, Co) have been extensively studied regarding magnetic configurations and site preference of the different metallic elements.