Dimensional Influence on the Vortex Movement in Superconducting YBa₂Cu₃O_7-δ Quasi-One-Dimensional Microwires

Vortex dynamics is a fundamental issue both, concerning superconducting applications at the macroscopic level (wires, magnets, …) ant at the small scale (superconducting microelectronics). Generally speaking, the basic conceptual scheme where the theory of vortex interactions is established, has been mainly associated to the configuration with the electric current density locally oriented perpendicular to the magnetic field. Thus, the physical framework that quantifies the appearance of resistive states builds upon the concept of a ``Lorentz-like’’ drag force on the vortex lines.<br/>In this work, thin nanometric layers of YBCO deposited by pulsed laser deposition (PLD) have been microstructured by means of optical lithography as microwires of 4um width, 1mm length and from 60 to 100nm thick. Isothermal magnetoresistance curves have been measured at low magnetic fields from 0 to 0.8 T for different configurations depending on the orientation between applied magnetic field, current density and sample dimensions at temperatures close to the critical value (). According to our observations, in these conditions, dissipation may be related to the flux dynamics through the interplay of: (i) conventional drag forces, (ii) thermoelectric effects, (iii) pinning by structural defects, and (iv) dimensional effects induced by flux quantization and the size of the sample. The enhancement of one phenomenon or another may be tuned through the relative orientation of field, current density, and sample. In particular, the experimental magnetoresistance curves show oscillations (figure 1) which can be related to the entrance of individual vortex arrays, as shown by their periodicity in terms of characteristic fields. This shows that microstructuration acquires a fundamental role for the investigation of vortex physics.