Implications of magnetic-hysteresis-loop scaling in high-temperature superconductors

Abstract

We show how to incorporate the commonly observed scaling behavior of magnetic hysteresis loops M(H) in (R)Ba2Cu3O7−δ (R=rare earth) crystals into a systematic and straightforward analytical procedure that yields the key parameters associated with the vortex dynamics. If the effective barrier height for vortex motion is written in terms of a scale energy U0(B,T) and a scale current density J0(B,T), both the field and temperature dependences of these quantities can be found directly from the experimental data, without any deconvolution. The procedure is illustrated with the data on one specific sample of TmBa2Cu3O7−δ. Over a substantial region of the B-T plane, J0(B,T) is found to be ∝B and essentially temperature independent; U0(B,T) is approximately ∝1/B and decreases steadily as Tc is approached. The competition between the field dependences of J0(B,T) and U0(B,T) gives rise to the ubiquitous ‘‘fishtail’’ in the magnetization loops.

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