Long columns and vortex mobility: a case study in NBCO films
NdBa2Cu3O7- (NBCO) thin films (2000 Å) grown by excimer KrF laser were irradiated with Au+13 (200 MeV) ions at doses equivalent to `matching field' ranging from 1 T to 4 T. Atomic force microscope (AFM) and scanning electron microscope (SEM) studies show significant topological changes consequent to heavy ion irradiation. Magnetization measurements were done with a SQUID magnetometer at different ambient temperatures. There is almost a four-fold increase in Jc, at the optimum ion dose, indicating a robust vortice pinning. The emergence of a diffused peak at the `matching field' value in the optimum flux data is a salient feature. We explain the morphological changes in the framework of existing models. We also suggest that the overriding peak in Jc is the signature of a process similar to the self-organized criticality of a sand pile - a common occurrence in nature.
Document Type: Miscellaneous
Jai Hind College, Mumbai 20, India
Bhabha Atomic Research Centre, Mumbai 85, India
Nuclear Science Centre, Delhi 67, India
Tata Institute of Fundamental Research, Mumbai 5, India
Publication date: January 1, 2002