Magnetic-domain-controlled vortex pinning in a superconductor/ferromagnet bilayer

Vortex pinning in a type-II superconducting Pb film covering a Co/Pt multilayer with perpendicular magnetic anisotropy is investigated. Different stable magnetic domain patterns like band and bubble domains can be created in the Co/Pt multilayer, clearly influencing the vortex pinning in the superconducting Pb layer. Most effective pinning is observed for the bubble domain state. We demonstrate that the pinning properties of the superconductor/ferromagnet bilayer can be controlled by tuning the size, density and magnetization direction of the bubbles.Comment: 4 pages, 3 figures, accepted for AP

Development of an oximeter for neurology

Cerebral desaturation can occur during surgery manipulation, whereas otherparameters vary insignificantly. Prolonged intervals of cerebral anoxia can cause seriousdamage to the nervous system. Commonly used method for measurement of cerebral bloodflow uses invasive catheters. Other techniques include single photon emission computedtomography (SPECT), positron emission tomography (PET), magnetic resonance imaging(MRI). Tomographic methods frequently use isotope administration, that may result inanaphylactic reactions to contrast media and associated nerve diseases. Moreover, the high costand the need for continuous monitoring make it difficult to apply these techniques in clinicalpractice. Cerebral oximetry is a method for measuring oxygen saturation using infraredspectrometry. Moreover reflection pulse oximetry can detect sudden changes in sympathetictone. For this purpose the reflectance pulse oximeter for use in neurology is developed.Reflectance oximeter has a definite advantage as it can be used to measure oxygen saturation inany part of the body. Preliminary results indicate that the device has a good resolution and highreliability. Modern applied schematics have improved device characteristics compared withexisting ones

Little-Parks effect and multiquanta vortices in a hybrid superconductor--ferromagnet system

Within the phenomenological Ginzburg-Landau theory we investigate the phase diagram of a thin superconducting film with ferromagnetic nanoparticles. We study the oscillatory dependence of the critical temperature on an external magnetic field similar to the Little-Parks effect and formation of multiquantum vortex structures. The structure of a superconducting state is studied both analytically and numerically.Comment: 7 pages, 1 figure. Submitted to J. Phys.: Condens. Mat

Asymmetric flux pinning in laterally nanostructured ferromagnetic/superconducting bilayers

We investigated the pinning of flux lines in a superconducting film by a regular array of magnetic antidots. The sample consists of a Co/Pt multilayer with perpendicular magnetic anisotropy in which a regular pattern of submicron holes is introduced and which is covered by a type-II superconducting Pb film. The resulting ferromagnetic/superconducting heterostructure shows a pronounced asymmetric magnetization curve with respect to the field polarity. This asymmetry clearly demonstrates that the magnetic contribution dominates the pinning potential imposed by the magnetic antidots on the superconducting film.Comment: 7 pages, 6 figures, including erratum with 1 page, 1 figur