Tuning Flux Pinning in GdBa2Cu3O7–x/La0.7Sr0.3MnO3 Epitaxial Bilayers via Substrate-Induced Strain

Abstract

The epitaxial bilayer systems consisting of GdBa2Cu3O7–x (GdBCO) and La0.7Sr0.3MnO3 (LSMO) grown on (001) SrTiO3 (STO) and LaAlO3 (LAO) substrates have been fabricated to study the correlation of magnetic flux pinning with substrate-induced strain state examined by X-ray absorption spectroscopy (XAS). Strain-dependent distortions of the MnO6 octahedron are clearly observed in both cases. In the bilayer system on the STO substrate, a weak elongation of the in-plane MnO6 octahedron and a reduction in the magnetization anisotropy of LSMO are observed by substrate-induced tensile strain. In contrast, a large elongation of the out-of-plane MnO6 octahedron and a large magnetic anisotropy are observed for the bilayer system on the LAO substrate that is under compressive strain. The flux pinning analyses of the two systems reveal that magnetic pinning effectively works with a small magnetic anisotropy. For the system under strong compressive strain, not only the magnetic pinning induced by LSMO but also additional flux pinning by structural distortion play a role in the pinning mechanism. These findings suggest a possibility of an active tuning of magnetic pinning by the ferromagnetic layer through a controlling of substrate-induced strain state.