We report on a new, relatively simple, magnetic method to determine the dominant pinning mechanism: Spatial fluctuations of the transition temperature Tc ("δTc-pinning") or of the charge carrier mean free path ℓ ("δℓ-pinning"). The method is based on measuring the magnetization curves in the range of the second anomalous peak, identifying the field Bss which signifies the vortex solid-solid transition. The qualitative temperature dependence of Bss determines the pinning mechanism: Bss increasing (decreasing) with T indicates δℓ-pinning (δTc-pinning). Using this method we have determined the pinning mechanism in YBa2Cu3O7-δ and Nd1.85Ce0.15CuO4-δ crystals to be δl-pinning and δTc-pinning, respectively.
Bibliographical noteFunding Information:
This work was partially supported by The Israel Science Foundation founded by the Israel Academy of Sciences and Humanities–Center of Excellence Program, and by the Heinrich Hertz Minerva Center for High Temperature Superconductivity. Y.Y. and A.S. acknowledge support from the German Israeli Foundation. D.G. acknowledges support from the Clore Foundation.
- Vortex phase transitions