Vibrating-reed studies of flux pinning in the superconducting metallic glass Zr70Cu30

Abstract

With the vibrating-reed technique we have measured the resonance frequency and damping of superconducting ribbons of a Zr70Cu30 amorphous alloy as a function of magnetic field and temperature for different heat treatments of the same sample. Through these measurements we obtain the Labusch parameter α in the reduced-field (b) range 5×10−4b=0.1, α=(3.8×1011)Bc2(T)2.15 N m−4 T−2.15, a result which is in agreement with the absolute value and temperature dependence of the pinning force obtained from critical-current measurements. The effect of annealing below the glass transition temperature is to produce changes in α which depend on field and temperature in a complicated fashion. There are indications that surface pinning could be important in these samples.