Dynamic and static mechanical measurements of flux-lattice softening and associated hysteretic depinning dissipation peak in YBa2Cu3Ox ceramic

Abstract

We have studied flux-lattice dissipation in YBa2Cu3Ox ceramic using a forced inverted torsional pendulum. Reversible restoring force variations during temperature sweep suggest that flux lines experience a "hard-soft" transition between 50 K and Tc. Measurements of internal friction and modulus change as a function of the applied stress show a typical depinning behaviour. This dissipation peak during the temperature sweep is understood as a hysteretic depinning in which the critical force depends upon the penetration depth.