Unusual magneto-transport of YBa₂Cu₃O_7−δfilms due to the interplay of anisotropy, random disorder and nanoscale periodic pinning

Abstract

We study the general problem of a manifold of interacting elastic lines whose spatial correlations are strongly affected by the competition between random and ordered pinning. This is done through magneto-transport experiments with YBa 2 Cu 3 O 7−δ thin films that contain a periodic vortex pinning array created via masked ion irradiation, in addition to the native random pinning. The strong field-matching effects we observe suggest the prevalence of periodic pinning, and indicate that at the matching field each vortex line is bound to an artificial pinning site. However, the vortex-glass transition dimensionality-quasi-two dimensional instead of the usual three dimensional-evidences reduced vortex-glass correlations along the vortex line. This is also supported by an unusual angular dependence of the magnetoresistance, which greatly differs from that of Bose-glass systems. A quantitative analysis of the angular magneto-resistance allows us to link this behaviour to the enhancement of the system anisotropy, a collateral effect of the ion irradiation.

Large pinning forces and matching effects in YBa2Cu3O7-δ thin films with Ba2Y(Nb/Ta)O6 nano-precipitates

“…For both samples, the N value maxima (and hence minima in S ) appear once reaches the matching field just the same as for J c at . A similar effect has recently been observed by Trastoy et al 58. on YBCO films with a periodic square pattern of artificial pin holes produced by ion irradiation.…”

Dynamics of vortex matter in YBCO sub-micron bridges

“…Resistive transition RðTÞ, current voltage characteristics (I-V) and magnetoresistance (MR) measurements are well established tools to decode some aspects of vortex dynamics. RðTÞ curves give information on the mechanisms and energy scales related to the onset of the superconducting state [15,16] while either I-V curves [17] or MR's [7][8][9][10] can provide information on vortex lattice deformations and/or phase transitions as function of frustration (i.e. the injected current or an external magnetic field) [1,2].…”

Unconventional critical state in YBa2Cu3O7−δthin films with a vortex-pin lattice fabricated by masked He+ion beam irradiation

“…For convenience we use n = 0 to denote the absence of vortices, n < 0 for reversed vortex orientation, and B n for the position of peaks or minima that are related to matching conditions. Such commensurability between fluxons and artificial pinning arrays have been observed in several electrical transport experiments in both metallic [27,28,29] and cuprate superconductors [30,31,32,9,10,11,33,12]. The peaks of I c can be understood as a consequence of two different vortex pinning mechanisms.…”

“…The peaks of the virgin curve after ZFC are displaced to lower field values which is an indication of both demagnetization effects in our thin YBCO films and strong irreversibility. Note that previous transport measurements in superconductors with regular pinning arrays showed no [27,29,31,32,9,10] or only slight [28,30] indications of irreversibility. In a thin superconducting film, demagnetization effects provoke an overshoot of the external magnetic field at the edges of the sample leading to a breakdown of the Meissner state even in very small fields and to the penetration of vortices.…”