Vibrating-reed studies of flux pinning in the superconducting metallic glass ${\mathrm{Zr}}_{70}$${\mathrm{Cu}}_{30}$

With the vibrating-reed technique we have measured the resonance frequency and damping of superconducting ribbons of a ${\mathrm{Zr}}_{70}$${\mathrm{Cu}}_{30}$ 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×${10}^{\mathrm{-}4}$b=0.1, α=(3.8×${10}^{11}$)${\mathit{B}}_{\mathit{c}2}$(T${)}^{2.15}$ N ${\mathrm{m}}^{\mathrm{-}4}$ ${\mathrm{T}}^{\mathrm{-}2.15}$, 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.