Direct evidence for the occurrence of superconductivity in the magnetic compound YFe4Al8

Анотація

For the first time we present the direct evidence for superconductivity in the ternary magnetic compound YFe₄Al₈ with the ThMn₁₂ type structure found via point-contact (PC) experiments on contacts between silver needle and single-crystal YFe₄Al₈, revealing the distinct Andreev-reflection current. The spectra measured prove the existence of normal-superconducting interface and exhibit the triangular-like shape in a vicinity of zero-bias voltage, inferring the unconventional type of superconductivity. The derived dependences of the order parameter versus temperature D(T) and m agnetic f ield D(H) are presented. D(T) follows BCS theory, whereas D(H) do not satisfy any theoretical predictions. In some cases there exists noticeable superconductivity enhancement by a weak magnetic field. The data obtained imply the v ery inhomogeneous distribution of superconductivity over the s ample volume in spite of its single crystal structure. We assume that the reason is associated with inherent magnetic inhomogeneities of this material. The highest values for the critical temperature T_c, upper critical magnetic field H_c2, and ratio 2D(0)/kT_c are 7.4 K, 5 T, and 7.2, respectively.