Features of Excess Conductivity Behavior in a Magnetic Superconductor Dy0.6Y0.4Rh3.85Ru0.15B4

The temperature dependencies of the excess conductivity sigma '(T) and possible pseudogap (PG), Delta*(T), in a Dy0.6Y0.4Rh3.85Ru0.15B4 polycrystal were studied for the first time. It was shown that sigma '(T) near T-c is well described by the Aslamazov-Larkin (AL) fluctuation theory, demonstrating a 3D-2D crossover with increasing temperature. Using the crossover temperature T-0, the coherence length along the c axis, xi(c)(0), was determined. Above the level of T-2D > T-0, an unusual dependence sigma '(T) was found, which is not described by the fluctuation theories in the range from T-0 to T-FM, at which a ferromagnetic transition occurs. The range in which superconducting fluctuations exist is apparently quite narrow and amounts to Delta T-fl approximate to 2.8 K. The resulting temperature dependence of the PG parameter Delta*(T) has the form typical of magnetic superconductors with features at T-max approximate to 154 K and the temperature of a possible structural transition at T-s similar to 95 K. Below T-s, dependence Delta*(T) has a shape typical for PG in cuprates, which suggests that the PG state can be realized in Dy0.6Y0.4Rh3.85Ru0.15B4 in this temperature range. Comparison of Delta*(T) with the Peters-Bauer theory made it possible to determine the density of local pairs near T-c, n(up arrow)n(down arrow)(TG) approximate to 0.35, which is 1.17 times greater than in optimally doped YBa2Cu3O7-delta single crystals.