Observation of fractional vortices and π phases in Josephson junctions involving periodic magnetic layers

I. P. Nevirkovets

doi:10.1103/PhysRevB.108.024503

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Observation of fractional vortices and π phases in Josephson junctions involving periodic magnetic layers

I. P. Nevirkovets

DOI 10.1103/PhysRevB.108.024503 · Physical Review B

T1

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Abstract

Characteristics of SN(F/N)nIN(F/N)mS Josephson junctions with n,m=1 to 3 are reported. Here, S is a superconductor (Nb), F is a magnetic material (nickel), N is a nonmagnetic metal (aluminum), and I is an insulator (Al/AlOx). The devices with n=m=1 and n=1,m=2 display critical current versus magnetic field [Ic(H)] dependences that imply the appearance of fractional magnetic vortices in the junction, corresponding to a half of the flux quantum. Stochastic switching between the two half-vortex polarities with emission of an integer vortex was observed. In the devices with n=m=3, a typical Ic(H) dependence consists of a background current with a large modulation period, and a Fraunhofer-like pattern with a small modulation period on top of the background current. The Fraunhofer-like pattern may be completely or partially inverted; in these states, there is a component of the Josephson current flowing against the bias current, indicating the presence of the π phase in the junction. The experiments give evidence that switching between the zero and π states can, potentially, be magnetically controlled.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown