28 research outputs found
Current-phase relation in Josephson junction coupled with a magnetic dot
The current-phase relation (CPR) for a short Josephson junction placed in the
nonuniform field of a small ferromagnetic particle is studied. The effect of
the particle produced on the junction appears to be strong due to the formation
of the pair of oppositely directed Abrikosov vortices which pierce the thin
film superconducting electrode and cause a small--scale inhomogeneity of
Josephson phase difference. The induced phase difference inhomogeneity is shown
to result in the nonzero fixed phase drop across the junction. The
equilibrium value corresponding to the ground state of the junction
depends the configuration of the vortex--antivortex pair. The possibility to
tune the ground state phase difference is discussed.Comment: 6 pages, 5 figure
Considerable enhancement of the critical current in a superconducting film by magnetized magnetic strip
We show that a magnetic strip on top of a superconducting strip magnetized in
a specified direction may considerably enhance the critical current in the
sample. At fixed magnetization of the magnet we observed diode effect - the
value of the critical current depends on the direction of the transport
current. We explain these effects by a influence of the nonuniform magnetic
field induced by the magnet on the current distribution in the superconducting
strip. The experiment on a hybrid Nb/Co structure confirmed the predicted
variation of the critical current with a changing value of magnetization and
direction of the transport current.Comment: 6 pages, 7 figure
Magnetic force microscope tip-induced remagnetization of CoPt nanodisks with perpendicular anisotropy
We report on the results of a magnetic force microscopy investigation of remagnetization processes in arrays of CoPt nanodisks with diameters of 35 and 200 nm and a thickness of 9.8 nm fabricated by e-beam lithography and ion etching. The controllable magnetization reversal of individual CoPt nanodisks by the magnetic force microscope (MFM) tip-induced magnetic field was demonstrated. We observed experimentally two essentially different processes of tip-induced remagnetization. Magnetization reversal of 200 nm disks was observed when the probe moved across the particle while in case of 35 nm nanodisks one-touch remagnetization was realized. Micromagnetic modeling based on the Landau-Lifshitz-Gilbert (LLG) equation demonstrated that the tip-induced magnetization reversal occurs through the essentially inhomogeneous states. Computer simulations confirmed that in case of 200 nm disks the mechanism of embryo nucleation with reversed magnetization and further dynamic propagation following the probe moving across the particle was realized. On the other hand one-touch remagnetization of 35 nm disks occurs through the inhomogeneous vortexlike state. Micromagnetic LLG simulations showed that magnetization reversal in an inhomogeneous MFM probe field has a lower energy barrier in comparison with the mechanism of coherent rotation, which takes place in a homogeneous external magnetic field