Diffuse scattering and image contrast of tweed in superconducting oxides: A simulation and interpretation

Monte Carlo simulations were performed with a lattice gas model which represents the interactions between oxygen atoms in YBa2 (Cu(1-x)M(x))(sub 3) O(7+delta) (M=Fe, Co, or Al, 0.03 less than x less than 0.1) system. The amplitudes of concentration waves/displacement waves obtained from these simulations were then used to calculate the intensity of the diffuse scattering of tweed seen in the electron diffraction pattern. The characteristic features of the tweed image were produced by calculation, using a model based on the contrast originating from structures with displacive modulation, stacking on the top of each other. Both calculations agree well with the TEM observations and provide a useful basis for a better insight into the origin of the tweed structure.