Magnetocrystalline Anisotropy In Rare-earth-Fe Compounds And Their Hydrides And The Calculation Of The Band Structure Of TiO₂

A rare-earth-transition metal intermetallic compound is a candidate for excellent permanent materials when it fulfills the following conditions: it must has a large spontaneous magnetization, a strong uniaxial magnetocrystalline anisotropy and a high magnetic ordering temperature . In thesis, the magnetic properties of several R-T compound ate studied by comparison of calculations with a series of experiments. The experiments include the temperature dependence of saturated magnetization for the single crystal, the magnetization curves along the crystal axes at a series of temperature. The manetocrystalline anisotropy of the rare-earth ion in the intermatallic compound originates from the crystal-field splitting of the 4f-shell. The values of the crystalline-electric-field (CEF) parameters at the rare-earth sites are usually obtained by fitting the magnetization curves for the single crystal. In this work, the high field magnetization curves for a series of single crystal R₂Fe₁₇( H₃)(R= Er,Tb,Ho) and magnetization curves for single crystal Er₂Fe₁₇ under high pressure were calculated on the basis of the single-ion model. The values of the exchange field and crystalline-electric-field parameters, H ex and An m in the calculations are obtained from best fit of the calculation to the experiments curves. According to the calculations, we found that the insertion of H and high pressure significantly change the values of crystalline-electric-field (CEF) parameters An m, which show that the insertion of H and high pressure significantly change the anisotropy of R ions. The study of Gd Mossbauer spectroscopy of the Gd 2 Fe17Hx (x=0,3,5)has been found that the insertion of H lowered the positive electric field gradient at the Gd nuclei in contrast to carbon and nitrogen insertion and the decrease of the crystal field induced anisotropy in the R2 Fe17H3compounds. Our calculation also shows that the sixth-order CEF parameter A60 plays a dominant role in reproducing the observed type-â…¡fist-order magnetization process (FOMP). The changes of the values of CEF under high pressure are smaller than that of the insertion of H . High pressure can make crystal lattice constant small. So this influence the distributing of electric cloud, and make the changes of CEF. the insertion of H not only make the crystal lattice constant expand to influence the distributing of electric cloud, but also H atom also influence the the distributing of electric cloud. So the changes of the values of CEF because of the insertion of H are bigger than that under high pressure. TiO2 is one of the many functional material . It may be used in energy-store and conversion processes, in antichalking agents in the paint and polymer industry, as a catalyst in the photocatalytic treatment of waste water. Its use in waste is one of the most use, in this process TiO2 is as a catalyst. This application depend on the transfer of electrons from the conduction band...