Visualizing supercurrents in ferromagnetic Josephson junctions with various arrangements of 0 and πsegments

Abstract

Josephson junctions with ferromagnetic barrier can have positive or negative critical current depending on the thickness $d_F$ of the ferromagnetic layer. Accordingly, the Josephson phase in the ground state is equal to 0 (a conventional or 0 junction) or to $\pi$ ($\pi$ junction). When 0 and $\pi$ segments are joined to form a "0-$\pi$ junction", spontaneous supercurrents around the 0-$\pi$ boundary can appear. Here we report on the visualization of supercurrents in superconductor-insulator-ferromagnet-superconductor (SIFS) junctions by low-temperature scanning electron microscopy (LTSEM). We discuss data for rectangular 0, $\pi$, 0-$\pi$, 0-$\pi$-0 and 20 \times 0-$\pi$ junctions, disk-shaped junctions where the 0-$\pi$ boundary forms a ring, and an annular junction with two 0-$\pi$ boundaries. Within each 0 or $\pi$ segment the critical current density is fairly homogeneous, as indicated both by measurements of the magnetic field dependence of the critical current and by LTSEM. The $\pi$ parts have critical current densities $j_c^{\pi }$ up to $35\units{A/cm^2}$ at $T = 4.2\units{K}$, which is a record value for SIFS junctions with a NiCu F-layer so far. We also demonstrate that SIFS technology is capable to produce Josephson devices with a unique topology of the 0-$\pi$ boundary.

29 pages, 8 figures

References in corpus (31)

• Coupling of two superconductors through a ferromagnet : evidence for a pi-junction
• Quiet SDS Josephson Junctions for Quantum Computing
• Supercurrent reversal in quantum dots
• Oscillations of the superconducting critical current in Nb-Cu-Ni-Cu-Nb junctions
• Half-integer Shapiro steps at the 0-pi crossover of a ferromagnetic Josephson junction
• 0-pi Josephson tunnel junctions with ferromagnetic barrier
• Josephson junctions with negative second harmonic in the current-phase relation: properties of novel varphi-junctions
• Superconducting pi qubit with a ferromagnetic Josephson junction
• Periodic alternating $0,\pi$-junction structures as realization of $\varphi$-Josephson junctions
• Critical Current 0-$\pi$ Transition in Designed Josephson Quantum Dot Junctions
• High quality ferromagnetic 0 and pi Josephson tunnel junctions
• Spontaneous supercurrent induced by ferromagnetic pi-junctions
• Josephson tunnel junctions with strong ferromagnetic interlayer
• Dynamics of semifluxons in Nb long Josephson 0-pi junctions
• Semi-fluxons in long Josephson 0-pi-junctions
• Static and dynamic properties of 0, pi, and 0-pi ferromagnetic tunnel Josephson Junctions
• Ground state and bias current induced rearrangement of semifluxons in 0-pi long Josephson junctions
• Phase-sensitive order parameter symmetry test experiments utilizing Nd2-xCexCuO4-y/Nb zigzag junctions
• Magnetic interference patterns in 0-Pi SIFS Josephson junctions: effects of asymmetry between 0 and Pi regions
• Observation of a controllable PI-junction in a 3-terminal Josephson device
• Superconducting pi qubit with three Josephson junctions
• Anti-ferromagnetic ordering in arrays of superconducting pi-rings
• Analytical analysis of ground states on 0-$\pi$ long Josephson junctions
• Fluxon-semifluxon interaction in an annular long Josephson 0-pi-junction
• Spectroscopy of the fractional vortex eigenfrequency in a long Josephson 0-kappa junction
• Ferromagnetic 0-pi Junctions as Classical Spins
• The 0 and the pi phase Josephson coupling through an insulating barrier with magnetic impurities
• Direct demonstration of circulating currents in a controllable $\pi$-SQUID generated by a 0 to $\pi$ transition of the weak links
• Semifluxon molecule under control
• Imaging of order parameter induced $\pi$ phase shifts in cuprate superconductors by low-temperature scanning electron microscopy
• Thermal escape of fractional vortices in long Josephson junctions

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