Upper Critical and Irreversibility Fields in Ba(Fe_0.95Ni_0.05)₂As₂ and Ba(Fe_0.94Ni_0.06)₂As₂ Pnictide B

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• 作者：Martin Nikolo ; John Singleton…
• 关键词：Upper critical magnetic field ; Irreversibility magnetic field ; Superconductors ; Pnictides ; Radio frequency proximity detector oscillator (PDO) measurement
• 刊名：Journal of Superconductivity and Novel Magnetism
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：30
• 期：2
• 页码：331-341
• 全文大小：
• 刊物类别：Physics and Astronomy
• 刊物主题：Strongly Correlated Systems, Superconductivity; Magnetism, Magnetic Materials; Condensed Matter Physics; Characterization and Evaluation of Materials;
• 出版者：Springer US
• ISSN：1557-1947
• 卷排序：30

文摘

A comprehensive study of upper critical and irreversibility magnetic fields in Ba(Fe_0.95Ni_0.05)₂As₂(large grain and small grain samples) and Ba(Fe_0.94Ni_0.06)₂As₂, polycrystalline bulk pnictide superconductors was made in pulsed fields of up to 65 T. The full magnetic field-temperature (H − T) phase diagrams, starting at 1.5 K, were obtained. The higher temperature, upper critical field H_c2 data are well described by the one-band Werthamer, Helfand, and Hohenberg (WHH) model. The large values of the Maki parameter α indicate that the Zeeman pair breaking dominates over the orbital pair breaking and spin-paramagnetic pair-breaking effect is significant in these materials. At low temperatures, the experimental data depart from the fitted WHH curves, suggesting an emergence of a new phase that could be attributed to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. Possible multi-band structure of these materials is lumped into effective parameters of the single-band model.