Superconducting fluctuation effect on epitaxially layered films of superconductor NbN and half-metallic Heusler alloy CoMnSi

Shigeta, Iduru*; Oku, Shuta*; Kubota, Takahide*; Kimura, Shojiro*; Seki, Takeshi*; Shinozaki, Bunju*; Awaji, Satoshi*; Takanashi, Koki; Hiroi, Masahiko*

Superconducting properties were investigated in epitaxially layered films consisting of superconductor NbN and half-metallic Heusler alloy CoMnSi(CMS). Temperature dependence of the electrical resistivity (T) was measured by applying perpendiar magnetic fields to the surface of NbN/CMS films. With the increase of the CMS thickness , the upper critical field H decreased monotonically, but the superconducting transition temperature T had the minimum of 10.1 K at 5 nm. The T behavior was in qualitative agreement with the theory of the -coupling. The pair-breaking parameter determined by the superconducting fluctuation theory took the maximum at = 35 nm, which would be related to the minimum of . The experimental results reveal that the superconductivity of the NbN layer in NbN/CMS films is affected by the interplay between the superconducting NbN layer and the half-metallic CMS layer.