الفهرس | Only 14 pages are availabe for public view |
Abstract Basma El-Assy, Physics Dept., Faculty of Girls, Ain Shams University. The aim of this thesis is to perform a first-principles study on the electronic structure and magnetic properties of some rare-earthtransition metal compounds RT5 (R = Y, Gd and Sm, T = Co) and the compound with Boron RT4B (R=Sm, T=Co). Our calculations are carried out self-consistently and based on Density-Functional Theory (DFT) as implemented in the Wien2K electronic code. Energy dependence on the lattice parameter ratio c/a, total density of states (DOS) in each compound and each crystal site and the DOS in each effective state, and band structure in two different directions in the Brillouin zone are calculated and discussed by using the Wien2k code. We also report the total and local magnetic moments in these compounds. These properties are attained in the case of spin-polarized and spin-polarized with spin-orbit interactions. These calculations showed that YCo5, SmCo5 and SmCo4B are ferromagnets while GdCo5 is a ferrimagnet. In addition, by using the methods of classical statistical mechanics, we calculated the magnetization curves, the anisotropy field and the probability landscape at room temperature. Also, we discussed the dependence of the magnetization vector on the direction of the magnetic field, along and perpendicular to the easyaxis. These calculations are carried out by Mathematica package and showed that the c-axis is the easy axis of magnetization for these compounds and also these compounds have high anisotropy at room temperature. Our calculations are in a good agreement with other works. This thesis is composed of three chapters, an abstract and a conclusion section. In the first chapter, a brief history of the compounds is discussed together and a review of magnetism and of magnetic materials, magnetic interactions in rare earth transition metal and energy bands in solids are given in some details. This is followed by a survey of the theoretical investigation of the quantummechanical properties of systems with detailed explanation of Density Functional Theory (DFT) in chapter 2. The results are presented and discussed in chapter 3. Finally a conclusion on the work is made. |