Multilayered MgB2/Ni thin films on Si substrates by electron beam evaporation were fabricated to enhance the critical current density Jc in magnetic fields parallel to the surface. The magnetic field dependence of Jc of the multilayered MgB2/Ni thin films for B//surface shows a peak at the matching field. In the field angular dependence of Jc, a sharp peak appears at B//surface. These results indicate that Ni layers which have ferromagnetism act as two-dimensional pinning centers in multilayered MgB2/Ni thin films. The vortex glass-liquid transition temperature Tg and the pinning parameter m were evaluated from the E-J characteristics. The slope of the magnetic field dependence of m in the multilayered MgB2/Ni thin film under the matching field is larger than that over the matching field. In the Tg/Tc-B phase diagram, the remarkable enhancement of Tg for B//surface appears around the matching field. These features are characteristic behaviors for two-dimensional pinning centers.
- Multilayered thin films
- Two-dimensional pinning center
ASJC Scopus subject areas
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Energy Engineering and Power Technology
- Electronic, Optical and Magnetic Materials