  Muon-spin rotation (muSR) experiments are often used to study the magnetic
field distribution in type-II superconductors in the vortex state. Based on the
determination of the magnetic penetration depth it is frequently
speculated---also controversially---about the order-parameter symmetry of the
studied superconductors. This article reports on a combined muSR and
magnetization study of the mixed state in the cuprate high-temperature
superconductor La_{1.83}Sr_{0.17}CuO_{4} in a low magnetic field of 20 mT
applied along the c axis of a single crystal. The macroscopic magnetization
measurements reveal substantial differences for various cooling procedures.
Yet, indicated changes in the vortex dynamics between different temperature
regions as well as the results of the microscopic muSR experiments are
virtually independent of the employed cooling cycles. Additionally, it is found
that the mean magnetic flux density, locally probed by the muons, strongly
increases at low temperatures. This can possibly be explained by a non-random
sampling of the spatial field distribution of the vortex lattice in this
cuprate superconductor caused by intensified vortex pinning.

Superconductivity