Abstract We report the magnetic properties of CaFe2As2, CaFe1·9Pt0·1As2, and Ca0·9La0·1Fe1·9Pt0·1As2 compounds in a wide temperature range of 5–300 K in the field up to 9 T. We have observed a well-defined anomaly in the resistivity around 165 K, which manifests clearly a well-known first order magneto structural phase transition from paramagnetic-tetragonal (T) state to antiferromagnetic orthorhombic (Ort) one. Pt doped and Pt and La co-doped CaFe2As2 samples exhibit a Kondo lattice behavior. The critical current density, Jc, and normalized pinning force Fp/Fp,max as a function of the applied field are obtained. Moreover, the normalized pinning force density, Fp/Fp,max curves versus h = H/Hirr were scaled using the Dew-Hughes model. Hence, the natures of the flux-pinning centers for these samples are revealed. Based on the results obtained from these analyses, we claim that the superconductivity in as-prepared CaFe2As2 occurs on the grain-boundary with the filamentary character.

中文翻译：

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Pt 和 La 掺杂对 CaFe2As2 超导性的影响：Kondo 效应

摘要 我们报告了 CaFe2As2、CaFe1·9Pt0·1As2 和 Ca0·9La0·1Fe1·9Pt0·1As2 化合物在 5-300 K 的宽温度范围内高达 9 T 的磁性能。在 165 K 附近定义了电阻率异常，这清楚地表明了众所周知的从顺磁 - 四方（T）状态到反铁磁正交（Ort）状态的一阶磁结构相变。Pt 掺杂和 Pt 和 La 共掺杂 CaFe2As2 样品表现出 Kondo 晶格行为。获得作为外加场函数的临界电流密度 Jc 和归一化钉扎力 Fp/Fp,max。此外，使用 Dew-Hughes 模型对标准化钉扎力密度、Fp/Fp,max 曲线与 h = H/Hirr 进行缩放。因此，揭示了这些样品的通量钉扎中心的性质。