L. Gozzelino et al., Investigation of the vortex confinement mechanisms in melt-textured YBa2Cu3O7-x with ion-induced surface nanostructuring, PHIL MAG B, 80(5), 2000, pp. 1025-1038
In the present paper the magnetic properties of high-quality melt-textured
YBa2Cu3O7-x irradiated with 2 GeV gold ions are studied. The irradiation af
fects a surface layer of 50 mu m (about 10% of the whole sample thickness),
while linearly correlated columnar defects are estimated to be present up
to about 46 mu m. The paper is focused on the magnetic property analysis of
the material before and after irradiation, as determined by the competitio
n and/or correlation between surface columnar defects and intrinsic defects
. In the intermediate- and high-temperature regions (T > 45 K), the surface
columnar defects are very effective according to critical current density
J(c), pinning force F-p, creep rate and irreversibility line measurements.
In particular the detailed study of the F-p versus B curves at 75 K by mean
s of a modified Dew-Hughes model shows that, before and after irradiation,
several kinds of defect are effective in different field ranges. After irra
diation, the columnar defects greatly modify the full scenario near an acco
mmodation field lower than the dose equivalent field. This large effect cou
ld depend on the fact that, at least at higher temperatures, the strong pin
ning of the vortices in the surface layers induces easier confinement of th
e vortices trapped by volume and planar defects in deeper layers.