Ergg Garnet Magnetic Properties

The thesis reports the magnetic properties of erbium gallium gallate (ErGaG) under the high magnetic field by using quantum theory. The theoretical results are compared with the experimental ones, and the factors, whether they have effects on the magnetic anisotropy, have been discussed.Magnetism is one of the basic attributes of the substance. The theoretical investigation of magnetic material is beneficial to further research and exploit the new magnetic product in the experiment. As we know, applied magnetic field has strong influence on the magnetic properties and big magneto-optical characteristics. So in the recent years, high magnetic field has been the focus on experiment. In 1998, M.Guillot, a French physical scientist, reported the magnetic properties in single crystal ErGaG., which showed some specific properties, and aroused the research interest of many theoretical scientists. But in the current magneto-optical theory, there is some difficulty to calculate it in detail, for the complex microscopic structure of Er3+ ion and the high magnetic field up to 300KOe. So to date, the quantitative calculation by quantum theory has not been seen.This paper shows the investigation on the magnetic properties of the single crystal ErGaG under high magnetic field by quantum theory, and gains the magnetic anisotropy. It is in good agreement with the result of the experiment. Using quantum theory, taking the special microscopic structure of ErGaG into account, we calculate and analyse the splitting of the lowest level (4I15/2) according to the crystal field. As to the paramagnetic ErGaG, the whole maganetization is zero. The crystal energy levels will split further when the magnetic field is parallel to the especial four directions. We-gain the according wave function and the magnetization changing with the magnetic field. To obtain the mechanism, we find the temperature" contribution to the magnetic anisotropy. The change of the temperature have a main effect on the occupied probability to all theenergy levels. To the diverse crystal site, the probability is not identical. To some materials, the mixing of the different multiplets of the ground term will affect the arising of the magnetic anisotropy, but by the calculation of the ErGaG, we find the mixing has no effect on it..In the calculation, we found that indirect exchange of rare earth ion has vital function on the calculation of magnetization and magneto-optical properties. There is some difference between the calculated data and the theoretical data using the current theory. We think that the indirect exchange is in relation to the magnetic field, and gain the coefficient relevant to the applied field. The result calculated using the coefficient is in good agreement with the experimental result. That also further perfects the theory of the microscopic mechanism of leading to the anisotropy of ErGaG.