Direct observation of the vortex structure in high-Tc superconductors in tilted magnetic fields

Interplay between pinning energy and vortex interaction inYBa2Cu3OHerbsommer1, Nieva2, Luzuriaga3 2000Phys. Rev. B202160View full textAdd to dashboardCite

“…7͒ find that the effectiveness of the pinning by the TB's disappears for angles greater than ϳ45°in contrast to what we see above. We do not know the reason for the discrepancy, but it could be due either to a difference in the quality of the different samples or to the fact that the crystals of Grigorieva et al 7 have TB's in perpendicular directions which may decrease the overall pinning effectiveness in tilted fields. The effectiveness of the pinning at high angles is also surprising if one considers some theoretical estimates.…”

“…A second reason is the fact that several previous decoration studies make this a wellcharacterized material. [7][8][9][10] In our particular case, we study a sample with TB's oriented in only one direction. When tilting an external magnetic field with rotation axis in the ab planes and perpendicular to the twin boundary planes there is a systematic change in the vortex-vortex interaction ͑because of the an-isotropy͒ and in the effect of pinning by twin boundaries.…”

Evidence for vortex staircases in the whole angular range due to competing correlated pinning mechanisms

“…We observe this maximum for Hу1 T. The width of this peak, ϳ5°, is in the typical range of reported trapping angles for twins. [3][4][5]9,10 On the other hand, the fact that the peak is mounted over an inclined background implies that vortices are also trapped by the tracks. Thus vortices in this angular range contain segments both in the tracks and in the twins.…”

“…13 Many experiments have confirmed the directional pinning due to columnar defects, twins, and Cu-O planes. [1][2][3][4][5][6][7][8][9][10][11] Evidence for a locked-in phase arises from the observation of the transverse Meissner effect, 10 but a quantitative determination of L (H,T) for columnar defects had not been done until now. The introduction of columnar defects inclined with respect to the crystallographic axis has been used 1,[6][7][8]10,11 to discriminate their pinning effects from those due to twin boundaries, and from anisotropy effects.…”

“…As threedimensional vortex configurations cannot be directly observed, our knowledge is mostly based on the analysis of the angular dependence of magnetization, susceptibility, or transport data. [1][2][3][4][5][6][7][8][9][10][11] According to theoretical models, 12,13 when the angle between the applied field H and the defects is smaller than the lock-in angle L vortices remain locked into the defects thus producing a transverse Meissner effect. For tilt angles larger than L and smaller than a trapping angle T , vortices form staircases with segments pinned into different defects and connected by unpinned or weakly pinned kinks.…”