Study On X - Ray Diffusion Scattering Of MgO Single Crystal Point Defects

d0 ferromagnetic semiconductor seems most likely to be applied in spintronics device due to its ferromagnetism at high temperature, has caused widespread research. Generally, this kind of magnetism is considered to come from the defects in material, but systemic quantitatively study on the relationship between d0 magnetism and defects is seldom carried out. Research results showed that MgO single crystal with defects presented d0 ferromagnetism. The simple face centered cubic crystal structure of MgO single crystal helps people completely characterize its defect configuration. Therefore, the detailed point defect configuration combined with magnetic properties is helpful to reveal the mechanism of d0 ferromagnetism.In this paper, point defects configuration of irradiated MgO single crystal was investigated by means of X-ray diffuse scattering technique. Applying the obtained X-ray diffuse scattering intensity formula based on the theory of lattice dynamics, we calculated the X-ray diffuse scattering intensity caused by single crystal cubic defects and double-force defects in MgO single crystal.High-quality (001) oriented MgO single crystal after irradiation treatment by 60Co with dose of 100 kGy,150 kGy and 200 kGy was used in this paper. The measurement of X-ray diffuse scattering intensity near the 200 and 311 reciprocal lattice point of MgO single crystal was carried out at Beijing Synchrotron Radiation Facility diffuse scattering station at different temperature. Correlation analysis of measured reciprocal space mapping and calculated X-ray diffuse scattering intensity distribution curve showed that:(1) The experimental radial scattering intensity distribution curve near the [200] and [311] reciprocal vectors indicated weaker Bragg peak of MgO single crystal as the irradiation dose increased, which means that the irradiation treatment induced defects to reduce the perfection of lattice. (2) Bragg diffraction angle of irradiated MgO single crystal becomes smaller indicative of larger lattice parameter. The (311) diffraction peak of irradiated MgO single crystal with the dose of 200 kGy has been split, implying the formation of the complex defects. X-ray diffuse scattering mainly reflect weak distortion zone. In the weak distortion zone, the lattice parameter becomes larger due to interstitial atoms. (3) The reciprocal space mapping of 200 fits well with the calculation of the diffuse scattering intensity curve of double-force defects, indicating that<110> split interstitial atoms were introduced in irradiated MgO single crystal. According to the stability analysing of irradiation defects in MgO single crystal, it should also have<100> split interstitial atoms. The formation of interstitial atoms is always accompanied by vacancies production, therefore, vacancies must also exist in irradiated MgO single crystal. Huang diffuse scattering comes from strain region. As the strain region becomes larger, Huang diffuse scattering will be stronger. Compared with the interstitial atoms, the lattice distortion caused by vacancies is much smaller, and X-ray diffuse scattering intensity due to vacancy is weaker also. So X-ray diffuse scattering technique can barely give more information about vacancies.