Nonsymmetric current–voltage characteristics in ferromagnet∕superconductor thin film structures

Abstract

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Asymmetric critical current of niobium microbridges with ferromagnetic stripe

“…In our arrangement, the magnetic overlayer covers almost the entire length ͑90%͒ of the bridge and, unlike the geometry of Touitou et al, 9 extends on both sides of the bridge. An advantage of our arrangement comes from the fact that the demagnetizing factor of the Co stripe, due to the large aspect ratio, pins the direction of magnetization along the length of the stripe 13 ͑perpendicular to the Nb bridge length͒.…”

“…The asymmetry was, however, observed in only a small temperature window. Similarly, Touitou et al 9 observed asymmetry in the critical current of a microbridge patterned from a La 0.7 Sr 0.3 MnO 3 ͑LSMO͒/YBa 2 Cu 3 O 7 ͑YBCO͒ bilayer. They attributed the effect to the vertical component of the magnetic field created by the LSMO layer at the edge of the bridge: the net field was modified, depending on the relative orientation of moment of magnetic layer and bias current.…”

Tunability of the critical-current density in superconductor-ferromagnet hybrids

“…[1][2][3] One of the lines of research that is attracting more attention is the possibility of increasing the critical-current density J c of the SC by placing ferromagnetic components near or inside the SC. Many experiments are being carried out to study the effect of ferromagnetic parts on the J c of the SC, both in the transport case, that is, when a current is fed in the SC via an external source, [4][5][6] and in the magnetic case, in which current in the SC is induced by an external magnetic field H a . [7][8][9][10] Considering the magnetic case, it is known that in SCs the width of the hysteresis loop M͑H a ͒ is directly associated to the critical-current density J c ͑H a ͒ of the SC, 11,12 according to the critical-state model ͑CSM͒.…”

Transport critical-current density of superconducting films with hysteretic ferromagnetic dots

“…[3][4][5] Another way is to introduce an adequate additional magnetic field that can reduce the local one in superconducting regions. This additional field can be due to the presence of ferromagnetic materials (FMs) that can be located close to the superconductor [6][7][8] or even inside it. [9][10][11][12][13][14][15][16] The introduction of the FMs inside the SCs can also modify the intrinsic pinning and this is known as magnetic pinning.…”