Angular-dependent vortex pinning mechanisms in YBa2Cu3O7 coated conductors and thin films

Abstract

We present a comparative study of the angular dependent critical current density in YBa 2 Cu 3 O 7 films deposited on IBAD MgO and on single crystal MgO and SrTiO 3 substrates. We identify three angular regimes where pinning is dominated by different types of correlated and uncorrelated defects. We show that those regimes are present in all cases, indicating that the pinning mechanisms are the same, but their extension and characteristics are sample dependent, reflecting the quantitative differences in texture and defect density. In particular, the more defective nature of the films on IBAD turns into an advantage as it results in stronger vortex pinning, demonstrating that the critical current density of the films on single crystals is not an upper limit for the performance of the IBAD coated conductors.

Properties of recent IBAD–MOCVD coated conductors relevant to their high field, low temperature magnet use

“…This power-law region usually occurs between 0.1 T and 1 T [2]. Typically [19],  values lie between 0.5 and 0.6 [20][21][22][23] for pure YBCO films. However, BZO reduces  to 0.3 [23] or 0.35-0.39 [24] and even 0.19 [19] because of its very strong c-axis correlated pinning effects.…”

“…This must mean that additional pinning mechanisms have been introduced by the BZO at low temperatures which remove the strongly anisotropic high temperature pinning seen with BZO. Usually the angular scaling follows a generalized anisotropic scaling introduced by Blatter et al [17] and Civale et al [22] for a range as high as 60º away from the tape plane. Unfortunately it is precisely the next 30º where magnet designers are most concerned and we thus defer further discussion of properties near the tape plane to later work.…”

Theory and simulations on strong pinning of vortex lines by nanoparticles

“…While in the first superconducting cables the critical currents were limited by weak links, in the second generation superconducting wires based on aligned YBa 2 Cu 3 O 7 (YBCO) films this problem was mostly resolved and critical currents are determined by vortex pinning. An impressive progress has been made to enhance critical currents in these films using both isotropic [1][2][3][4][5][6][7] and columnar [8][9][10] inclusions. In spite of this progress, understanding of strong pinning mechanisms is far from satisfactory.…”

Strong pinning in very fast grown reactive co-evaporated GdBa2Cu3O7 coated conductors

“…This flat region is much less obvious for sample C. To extract the c axis component of J c from the angular data, the curves were fitted according to Blatter's anisotropic scaling approach. 19 According to this model, the J c 's of samples with uncorrelated point-like disorder depends only on a single variableĤ = H(cos( ) 2 +γ −2 sin( ) 2 ), where γ ∼ 5−7 is the electronic mass anisotropy. Thus, the measured J c ( , H) curves collapse together in the ( , H) regions where only random pinning is present when plotted as a function ofĤ.…”