In this work dependences of the electron band structure and spectral function in the HTSC cuprates on magnitude of electron-phonon interaction (EPI) and temperature are investigated. We use three-band p-d model with diagonal and offdiagonal EPI with breathing and buckling phonon mode in the frameworks of polaronic version of the generalized tight binding (GTB) method. The polaronic quasiparticle excitation in the system with EPI within this approach is formed by a hybridization of the local multiphonon Franck-Condon excitations with lower and upper Hubbard bands. Increasing EPI leads to transfer of spectral weight to high-energy multiphonon excitations and broadening of the spectral function. Temperature effects are taken into account by occupation numbers of local excited polaronic states and variations in the magnitude of spin-spin correlation functions. Increasing the temperature results in band structure reconstruction, spectral weight redistribution, broadening of the spectral function peak at the top of the valence band and the decreasing of the peak intensity. The effect of EPI with two phonon modes on the polaron spectral function is discussed.
The structural, magnetic and magneto-optical properties of Mn/RE/Bi (RE equals Nd, Eu, Cd, Tb, Dy) films prepared by multilayer technology are reported. The results of the investigations show that these films exhibit a smaller crystallite size, an improved squareness of the hysteresis loops, an enhanced Kerr rotation and a higher stability of the structural and magnetic properties than that of MnBi films. It is assumed that the specific influence of RE spacer layers on the structure is related with their atomic radius. The possible reasons of the Kerr effect enhancement in Mn/RE/Bi films were discussed: the increased matrix elements of the 6p-3d transitions, the significant polarization of Bi 6p band, the change of the density of states near the Fermi level. It was found that Mn/Dy/Bi films have best parameters: average crystallite size 15 nm, Hc equals 6 kOe, Ku equals 1 (DOT) 107 erg/cc, 2(Theta) k equals 4.5 degree(s), (Theta) k(root)R equals 1.5 degree(s) at (lambda) equals 633 nm. The wavelength dependent of Kerr rotation have the maximum in the region (lambda) equals 633 nm that represents the practical interest. The suitable properties of Mn/Dy/Bi films allow it to use it as a magneto-optical storage medium. The results of the thermomagnetic writing and magneto-optical readout in these films were presented.
It's shown in the framework ofthe multiband p-d model that formal Ni2 ion state is not a S1 d8 ion but is a mixture of d9 5=1/2 and d'° 5=0 configurations. High spin contribution is eliminated by strong electron correlations. We assume that for both Zn and Ni substitution the concentration dependence of TN and T is determined by the diamagnetic contribution to the impurity state and this assumption is in a good agreement with experimental data on 1 :2:3 and 2: 1 :4 systems.
The electronic structure in antiferromagnetic insulator Sr2CuO2Cl2 is calculated in the multi band p-d model of CuO2 layer with account for strong electron correlations. The results are in good agreement with recent ARPES data and are compared with the results of the t-J model. Spin fluctuations result in the anisotropy of the effective mass at the top of the valence band.
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