Abstract
The size-, surface- and proximity-effects are combined for calculating the critical temperature and some unusual electromagnetic properties of superfine superconducting NbTi filaments (i.e. with a diameterd s < 0·1 μm) in the neighbourhood of normal metal (Cu). It is shown that the existence of the one-dimensional flux line lattice is responsible for the extremely large values of the critical current densities in low magnetic fields (B < 0·2B c2,B c2 — the upper critical magnetic field), for the maximum of the volume pinning force at low magnetic fields (B m ≈ 0·1B c2, comparing withB m≈ 0·5B c2 in usual macroscopic multifilamentary NbTi superconductors), as well as for the peculiar minimum of the magnetization after reversing the magnetic field direction. The possible role of the frozen-in flux lines in creating flux lines of opposite direction is sketched. It is proposed that for practical purposes the superconducting filaments should be coated with electrically insulating material (e.g. cupro-nickel or dielectric) to destroy the electro-magnetic coupling between the filaments and to ensure low ac losses in the composite.
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Takács, S. Properties of superfine superconducting filaments embedded in normal matrix. Czech J Phys 36, 524–536 (1986). https://doi.org/10.1007/BF01597634
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DOI: https://doi.org/10.1007/BF01597634