Czechoslovak journal of physics vol:46 pages:2339-2340
Mesoscopic superconducting loops exhibit a well-known h/2e periodic modulation of the transition temperature T-c with the enclosed magnetic flux Phi, which is due to the fluxoid quantization. We have found substructures of this modulation in the magnetoresistance R(Phi) and the phase boundaries T-c(Phi) of microladders containing several square loops of 1.4 mu m size. The substructures are due to transitions between superconducting states differing in the order parameter profile and the flow pattern of the supercurrents. The experimental data are in excellent agreement with the theoretical phase boundaries obtained within the de Gennes-Alexander approach for superconducting micronetworks.