Irreversibility fields and critical current densities in strongly pinned YBa2Cu3O7-x films with BaSnO3 nanorods: The influence of segmented BaSnO3 nanorods

Abstract

We report irreversibility fields Birr and critical current densities Jc in YBa2Cu3O7-x thin films containing segmented BaSnO3 nanorods. Birr and Jc are systematically changed by selection of nanorod length and its spacing, and the variations are explained by the “harmonic oscillator” approach based on the Bose glass state. Analysis of pinning energies and Jc indicates that segmented nanorods behave as single columnar pin for B || c, in contrast, as nanoparticle pins for B || ab. The present results may help to further investigate anisotropy tuning of pinning structures.

Enhanced flux pinning in YBCO multilayer films with BCO nanodots and segmented BZO nanorods

“…It states that if the vortex goes along one pinning site in the c direction less than the standard deviation of the sideways step of the vortices, the peak disappears. Similar disappearance of the c peak has been seen on non-continuous BZO nanorods 25 and on BSO doped YBCO films with a multilayer structure of undoped YBCO in between 16 . However, as Matsumoto et al .…”

“…However, as Matsumoto et al . 16 pointed out, the ends of the nanorods are powerful for pinning in the ab direction.

Figure 3The angular dependence of the samples at ( a ) 10 K and 8 T, ( b ) 40 K and 4 T and ( c ) 77 K and 1 T. The c peak can be seen around θ  = 0°. A part of the data for m100 at 10 K is missing due to current limitations of the measurement system.

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“…Furthermore, it is remarkable that the nanorods in m250 have not grown on top of each other, unlike e.g. the rods in BSO doped YBCO rods with undoped YBCO in between 16 . The self-aligned growth has been attributed to strain fields created by the dopant 23 and since BCO itself tends to increase strain in YBCO 8,9 , it likely disturbs the rod formation process.…”

“…The segmented nanorods that are formed by depositing undoped YBCO between the layers of doped YBCO provide larger pinning force especially in the direction of B|| ab plane of YBCO, as compared to the continuous nanorods. In that direction, the ends of the nanorods actually pin stronger than any other defect 16 . Furthermore, by tuning the length of the segmented nanorods, the behaviour of J c in different magnetic fields and orientations can be greatly modified.…”

“…Thus, for the best result, application-related design is needed. In addition to mixing different types of dopants, multilayer structures containing layers of BZO doped YBCO 14,15 or BSO doped YBCO 16,17 along with layers of undoped YBCO have also been studied. The segmented nanorods that are formed by depositing undoped YBCO between the layers of doped YBCO provide larger pinning force especially in the direction of B|| ab plane of YBCO, as compared to the continuous nanorods.…”