کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5492276 | 1525672 | 2017 | 43 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Flux pinning properties of YBa2Cu3O7-δ thin films containing a high density of nanoprecipitates: A comparative study to reveal size effects
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
فیزیک و نجوم
فیزیک ماده چگال
پیش نمایش صفحه اول مقاله

چکیده انگلیسی
Temperature dependence of critical current density Jc(H, T) was measured in moderate magnetic fields (H ⥠film) in two thermally co-evaporated YBa2Cu3O7-δ (YBCO) thin films (A, B) and two YBCO films (C, D) deposited using a pulsed-laser deposition method. All sample films were grown epitaxially with the c-axis perpendicular to the surface of a single-crystalline substrate. Transmission electron microscopy observation revealed that these four films contained a high density of nanoprecipitates with typical sizes of 3.6 - 5.0â¯nm (A), 5.0 - 7.1â¯nm (B), 7.0 - 10.1â¯nm (C) and 8.7 - 14.3â¯nm (D). Films A and B contained very fine nanoprecipitates, whose typical diameters Dtyp are smaller than double the estimated Ginzburg-Landau coherence length 2ξab at Tâ¯=â¯77â¯K, and exhibited a steep increase of Jc with decreasing temperature. Whereas, film D, which contained relatively large nanoprecipitates (Dtypâ¯>â¯2ξab at Tâ¯â¤â¯70â¯K), exhibited a gradual increase in Jc. This led to a remarkable crossing of the Jc(T) curves. The temperature dependence of Jc(H//c) under a fixed magnetic field is approximated by Jc â¼Â (1 - T/Tc)m(1â¯+â¯T/Tc)2 where the index m is larger for films containing finer precipitates; that is, m(A)â¯>â¯m(B)â¯>â¯m(C)â¯>â¯m(D). This means that finer nanoprecipitates generally cause steeper Jc increase at low temperatures, which is the origin of the observed crossing phenomenon. The experimental results are reasonably explained by several theoretical models based on the direct summation of elementary pinning forces fp calculated by core pinning interactions.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physica C: Superconductivity and its Applications - Volume 542, 15 November 2017, Pages 46-54
Journal: Physica C: Superconductivity and its Applications - Volume 542, 15 November 2017, Pages 46-54
نویسندگان
Hirofumi Yamasaki, Hiroshi Yamada,