Low Temperature Vortex Dynamics in Superconducting Nb Films Containing Square and Rectangular Arrays of Ni Nanodots

C. E. CHILIOTTE, S. J. CARREIRA, V. BEKERIS, A. GÓMEZ, E. M. GONZALEZ, J. L. PRIETO AND J. L. VICENT

IEEE TRANSACTIONS ON MAGNETICS

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Lugar: New York; Año: 2013

0018-9464

We examine the vortex lattice (VL) dynamics in superconducting Nb films containing square and rectangular arrays of Ni nanodots, using ac susceptibility techniques. A remarkable robust feature is the increase in pinning that occurs for magnetic fields that create integer, n, or half integer flux lines per pinning cell. This phenomenology has been reported in transport experiments performed very close to the sample critical temperature, TC. In our contactless experiments we determined vortex mobility and pinning properties in an extended temperature range, 0.65 < T/ TC < 0.99. This was possible after growing larger samples, in the mm2 range, with top down techniques. For the square pinning array, matching up to n = 8 was observed and pinning for n = 3, 4 and 5 show different characteristics, in agreement with published simulations. For the rectangular array, some of the matching orders are missing and we do not find clear evidence of a reconfiguration transition, where vortex commensuration changes from a rectangular cell to a square cell, as reported near TC in earlier transport experiments.