Master Thesis Effect of vortex shaking on the ... - Physik-Institut

List <strong>of</strong> Figures
1 Shubnikov-Phase (“mixed state”) in a Type II superconductor
with the Abrikosov lattice. . . . . . . . . . . . . . . . . . . . . 3
2 Phase diagrams <strong>of</strong> a conventional low temperature and a high
T c type-II superconductor. . . . . . . . . . . . . . . . . . . . . 4
3 Visualization <strong>of</strong> the transverse and longitudinal <strong>vortex</strong> <strong>shaking</strong>.
In both geometries the vortices drift towards the center
<strong>of</strong> the strip. Shown is one <strong>vortex</strong> at subsequent times
tω/π = 0, 1, 2, . . . . Top: If h ac is transverse to J, the vortices
“walk” in the xz plane (the vortices are straight since here
J c ≪ h ac , H a is assumed). Bottom: If h ac is parallel to J, the
vortices periodically tilt in the yz plane and at the same time
move along x. From [15]. . . . . . . . . . . . . . . . . . . . . . 8
4 Scheme <strong>of</strong> the <strong>vortex</strong> shift in a slab when the longitudinal ac
magnetic field is increased from h ac to h ac + δh. Shown is
the projection on the xy plane <strong>of</strong> a <strong>vortex</strong> (bold solid line)
which tilts more away from the z axis and at the same time
shifts from x = x 0 to x = x 0 + δx 0 . The projected shifts <strong>of</strong>
some <strong>vortex</strong> line elements are shown as dashed arrows with
components δx 0 and δy(z), δy(z) = −δy(−z). These arrows
are along the Lorentz force, which is perpendicular to the local
current density j c (z) (solid arrows) lying in the xy planes at
the angle φ(z) to the y axis. From [15]. . . . . . . . . . . . . . 9
5 Structure <strong>of</strong> YBCO with the CuO 2 planes. In NdBCO the
Yttrium atoms are replaced by Neodymium. . . . . . . . . . . 10
6 Location <strong>of</strong> the melting transition in the magnetic phase diagram.
(Data from specific-heat measurements.) . . . . . . . . 10
7 Sketch <strong>of</strong> the experimental setup, side view. . . . . . . . . . . 11
8 Example <strong>of</strong> the first unsuccessful measurements at 0 Tesla,
where the resistance becomes “negative”. T c is at 96K. . . . . 13
9 Scattered data in the graph <strong>of</strong> the 9T (2/1000/0.1) measurement. 15
10 Results for the measurements <strong>of</strong> the resistance <strong>of</strong> NdBCO
without <strong>shaking</strong>. Background and <strong>of</strong>fset distracted. . . . . . . 16
11 Results for the measurements at 7T with and without <strong>shaking</strong>.
Upper right: Zoom into the region <strong>of</strong> the melting transition.
Crosses representing the run without <strong>shaking</strong>, stars the run
with <strong>shaking</strong>. Bottom: Difference between the normal and
the resistance with <strong>shaking</strong>. . . . . . . . . . . . . . . . . . . . 17
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