Oh J Y, Song C Y, Ko Y J, Lee J M, Kang W N, Yang D S, Kang B
Department of Physics, Chungbuk National University Cheongju Korea
Department of Physics, Sungkyunkwan University Suwon Korea.
RSC Adv. 2020 Oct 26;10(64):39102-39108. doi: 10.1039/d0ra06431a. eCollection 2020 Oct 21.
The effect of magnetic flux pinning is investigated in GdBaCuO (GdBCO) thin films with two different types of ferromagnetic LaSrMnO (LSMO) buffers (nanoparticles and a layer) deposited on an STO substrate. Magnetization analyses reveal the presence of multiple flux pinning mechanisms responsible for the improvement in the critical current density of GdBCO films. While core pinning becomes a dominant pinning mechanism in GdBCO films with LSMO nanoparticles, a hybrid effect of magnetic-volume and core-point pinning is observed in GdBCO films with LSMO layers. Examinations of local structures for both LSMO and GdBCO using extended X-ray absorption fine structure spectroscopy (EXAFS) exhibit a close relation between the parameters in the pinning force scaling and the length ratio of the Mn-O bond to the Cu-O bond. This result implies that the origin of core pinning is probably attributed to epitaxial strain induced by lattice mismatch between LSMO and GdBCO. Therefore, an appropriate strain state of LSMO is required for an effective operation of magnetic pinning.
在沉积于STO衬底上的具有两种不同类型铁磁LaSrMnO（LSMO）缓冲层（纳米颗粒和一层薄膜）的GdBaCuO（GdBCO）薄膜中，研究了磁通钉扎效应。磁化分析揭示了存在多种磁通钉扎机制，这些机制导致了GdBCO薄膜临界电流密度的提高。虽然在具有LSMO纳米颗粒的GdBCO薄膜中，核心钉扎成为主导钉扎机制，但在具有LSMO层的GdBCO薄膜中观察到了磁体积和核心点钉扎的混合效应。使用扩展X射线吸收精细结构光谱（EXAFS）对LSMO和GdBCO的局部结构进行检查，结果表明钉扎力标度中的参数与Mn - O键和Cu - O键的长度比之间存在密切关系。这一结果表明，核心钉扎的起源可能归因于LSMO和GdBCO之间晶格失配引起的外延应变。因此，为了有效发挥磁钉扎作用，需要LSMO处于适当的应变状态。
