Superconducting properties of amorphous MoX (X = Si, Ge) alloy films for Abrikosov vortex memory

Structural and superconducting properties of amorphous MoSi (∼55%Si) and MoGe (∼30% Ge) films (200 and 50 nm in thickness) prepared by rf magnetron sputtering were examined for the purpose of application to Abrikosov vortex memory devices. Amorphous single-phase films were obtained at concentrations of 20% Si and above, while a crystalline phase was detected even at a concentration of 30% Ge. The highest critical temperature T/sub c/ was 7.2--7.3 K in Mo-20% Si films. Magnetic penetration depth λ at 4.2 K and upper critical field dependence on temperature B/sub c/2(T) were measured. The B/sub c/2(T) behavior in the vicinity of T/sub c/ showed a tail-like shape, which most likely is the result of structural inhomogeneities in the prepared films. The λ dependence on Si concentration was satisfactorily explained through the Ginzburg--Landau--Abrikosov--Gorkov (GLAG) dirty limit theory using the corrected critical temperature T/sup *//sub c/ which is defined by the B/sub c/2(T) results. Other superconducting parameters (GL parameter κ/sub GL/ and coherence length ξ/sub GL/ ) and bare electronic density of states N(0) were derived from the GLAG relationships using the temperature slope of B/sub c/2(T). Flux pinning was examined through the critical current measurements at 4.2 K in the perpendicular applied field to the film surface. Preliminary results on edge pinning estimation were also presented