Vortex configurations and metastability in mesoscopic superconductors

Abstract

The vortex dynamics in mesoscopic superconducting cylinders with rectangular cross section under an axially applied magnetic field is investigated in the multivortex London regime. The rectangles considered range from a square up to an infinite slab. The flux distribution and total flux carried by a vortex placed in an arbitrary position of the sample is calculated analytically by assuming Clem's solution for the vortex core. The Bean-Livingston energy barrier is also analytically calculated in this framework. A Langevin algorithm simulates the flux penetration and dynamical evolution of the vortices as the external field is slowly cycled. The simulated magnetization process is governed by metastable states. The magnetization curves are hysteretic, with paramagnetic response in part of the downward branch, and present a series of peaks corresponding to the entry or expulsion of a single vortex. For elongated rectangles, the vortices arrange themselves into parallel vortex chains and an additional modulation of the magnetization, corresponding to creation or destruction of a vortex chain, comes out.

Magnetic instabilities along the superconducting phase boundary of Nb∕Ni multilayers

“…23͒ when N L vortices enter in successive chains aligned parallel to the ML and H ͑an average oscillation period of 70 mT implies 4 N L Ϸ 2 ϫ 10 3 ͒. Moreover, calculations 22,24,25 predict that a succession of vortex lattices will form within a thin SC slab in an increasing parallel field, and these phases will have different packing topologies whose ranges of stability may not be strictly periodic in applied field.…”

Superconductivity as a probe of magnetic switching and ferromagnetic stability in Nb/Ni multilayers

“…2b is determined by AC experiments with DC field-cooling, which would involve a different degree of equilibration. Calculations [26,46,47] predict that a succession of FL lattices will form as vortices penetrate a single, thin film superconductor in an increasing parallel field; but these phases will have different packing topologies whose ranges of stability may not be strictly periodic in applied field. This situation is at least qualitatively consistent with the anomalies shown in Fig.…”

Surface Effects on the Dynamic Behavior of Vortices in Type II Superconducting Strips with Periodic and Conformal Pinning Arrays

“…In these cases, the size effects play an important role. With this purpose, several authors investigated theoretically finite and semi-finite size systems with diverse geometries, using the Ginzburg-Landau [64][65][66][67][68][69][70][71][72][73][74][75] and London approach [76][77][78][79][80]. However, there are still open questions about critical depinning currents and vortex behavior in such systems, specially under the influence of pinning arrays.…”

“…For the particular case of superconducting strips, some works had been conducted investigating vortex states, critical currents, and magnetization curves [76][77][78][79][82][83][84][85][86][87][88][89][90]. In strips, vortices arrange themselves in chains of straight vortex lines due to the geometrical constraint [76], and the magnetization curves present several peaks, indicating the vortex lattice transitions with formation or destruction of the vortex chains [78,88].…”