Fizika Nizkikh Temperatur: Volume 45, Number 11 (November 2019), p. 1403-1414 ( to contents , go back )
Features of the excess conductivity behavior in a magnetic superconductor Dy0.6Y0.4Rh3.85Ru0.15B4
A.L. Solovjov, A.V. Terekhov, E.V. Petrenko, L.V. Omelchenko
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauki Ave., Kharkiv 61103, Ukraine
Superconducting Material Research Center (SMRC), Northwest Institute for Non-Ferrous Metal Research (NIN) Xi’an, China
Received June 24, 2019, published online September 27, 2019
The temperature dependences of the excess conductivity σ'(T) and the possible pseudogap (PG), Δ*(T), in the Dy0.6Y0.4Rh3.85Ru0.15B4 polycrystal have been studied for the first time. It was shown that σ'(T) near Tc is well described by the Aslamazov–Larkin (AL) fluctuation theory, demonstrating a 3D–2D crossover with increasing temperature. From the cross-over temperatureT0, the coherence length along the c axis, ξc(0), was determined. Above T2D > T0, an unusual dependence σ'(T) was found, which is not described by the fluctuation theories in the interval from T0 to TFM, at which a ferromagnetic transition occurs. The interval in which superconducting fluctuations exist is rather narrow and amounts to ΔTfl ≈ 2.8 K. The resulting temperature dependence of the PG parameter Δ*(T) has the form typical of magnetic superconductors with features at Tmax ≈ 154 K and the temperature of a possible structural transition at Ts ~ 95 K. Below Ts, Δ*(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 Δ*(T) with the Peters–Bauer theory made it possible to determine the density of local pairs near Tc, 〈n↑n↓〉(TG) ≈ 0.35, which is 1.17 times more than in optimally doped YBa2Cu3O7–δ single crystals.
Key words: superconductivity, magnetism, excess conductivity, pseudogap state, magnetization, local pairs.