SUPERCONDUCTIVITY, INCLUDING HIGH-TEMPERATURE SUPERCONDUCTIVITY: Andreev reflection study of the new magnetic superconductor Mo{sub}3Sb{sub}7 in magnetic field

摘要

Andreev reflection in contacts based on the magnetic superconductor Mo{sub}3Sb{sub}7 in a magnetic field is investigated by the point-contact method. It is found that the behavior of the order parameter in the magnetic field Δ(H) is essentially dependent on the value of A, which varies widely (Δ(0,0)≈0.01-0.31 meV) for different contacts at practically invariant T{sub}c. At high A the dependence Δ{sub}(max)(H) deviates slightly from the theoretical prediction applicable under point-contact conditions. As the order parameter decreases, the deviation starts to increase and becomes very large when A approaches its minimum. Proceeding from the results obtained in this study and from the temperature measurements on Mo{sub}3Sb{sub}7 performed previously, we are inclined as before to assign the compound to the class of superconductors with an anisotropic gap function. Therefore, in no way can it be considered as a conventional BCS-type superconductor. The upper critical field H{sub}(c2)≈ 16.5 kOe found here is close to that obtained from magnetization measurements in other studies. According to an estimate made, the pair-breaking effect of the Pauli paramagnetism is rather weak in Mo{sub}3Sb{sub}7.