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Results of X-ray absorption fine structure measurements in manganites (La 1-x Ho x ) 2/3 Ca 1/3 MnO 3 with 0.15 < x < 0.50 are presented. When LaMnO 3 is doped with a, divalent element such as Ca 2+ , substituting for La 3+ , holes are induced in the filled Mn d orbitais. This leads to a, strong ferromagnetic coupling between Mn sites. Ca ions in La 1-x Ca x MnO 3 introduce a distortion of the crystal lattice and mixed valence Mn ions (Mn 3+ and Mn 4+ ). On the other hand, in manganites (La 1-x Ho x ) 2/3 Ca 1/3 MnO 3 the substitution of La for Ho causes a lattice distortion and induces a disorder, which reduces a magnetic interaction. The ferromagnetic transition temperature and conductivity decrease very quickly with increasing x. The magnetic and transport properties of compounds depend on the local atomic structure around Mn ions. The information on the bond lengths and Debye-Waller factor are obtained from the extended X-ray absorption fine structure (EXAFS) data analysis. The charge state of Mn is determined from the position of the absorption edge in X-ray absorption near edge structure (XANES) data. XAFS results are in good agreement with magnetic characteristics of the studied materials.

Differential conductance G as a function of the bias voltage V was measured for break-junctions of superconducting Bi2Sr2CaCu2O8+δ and YBa2Cu3O7−δ. The dependences G(V ) for both materials clearly demonstrate the so-called dip–hump structures outside the gap region. A theory, which suggests the charge-density-wave origin of the dip–hump structures and explains its specific form by intrinsic inhomogeneity of cuprate materials, was developed. The well-known pseudogap features in the tunnel spectra of high-Tc oxides found both below and above the superconducting critical temperature are also described by the theory, which testifies that both the pseudogap and the dip–hump structures have the same origin. Competing theories and various G(V ) peculiarities found for a number of superconducting oxides are briefly discussed.

The voltage, V , dependences of the differential tunnel conductance G(V ) were calculated for two kinds of junctions involving normal and superconducting charge-density-wave metals (CDWMs) in the external magnetic field H. The first is a non-symmetrical junction with a CDWM electrode being biased with respect to a ferromagnet. Calculations show that the paramagnetic splitting occurs between spin-up and spin-down components of G(V ), similar to what is observed when a superconducting electrode is used instead of the CDWM one. The second setup is symmetric (CDWM– I–CDWM), where I denotes an insulator. If at least one of the CDWM electrodes is normal and H 6= 0, G(V ) will also be spin-split.