Studies on the proximity effect in Bi-based high temperature superconductor/manganite heterostructures

Abstract

A comprehensive study on the heterostructures of a Bi-based high critical temperature cuprate superconductor (Bi_1.75Pb_0.25Sr₂Ca₂Cu₃O_10+δ) and a Pr-based ferromagnetic manganite (Pr_0.6Sr_0.4MnO₃) has been elucidated. The heterostructures were optimized by an in-depth characterization of their structural and elemental properties using techniques such as X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The effect of proximity of the magnetism of the Pr_0.6Sr_0.4MnO₃ on the superconductivity of Bi_1.75Pb_0.25Sr₂Ca₂Cu₃O_10+δ has been established based on the results obtained from the magnetotransport and magnetization measurements. Furthermore, the electronic properties of the superconductor/ferromagnet bilayers and junctions have been thoroughly investigated from the perspectives of synthesis sequence, interface morphology, phase formation, crystallinity, interfacial interactions, proximity effects, strain, and magnetic properties. The observance of proximity-induced changes in the physical properties of the Pr_0.6Sr_0.4MnO₃/Bi_1.75Pb_0.25Sr₂Ca₂Cu₃O_10+δ heterostructure has been rationalized by considering the combined effect of magnetic exchange interaction arising from the manganite, the leakage of Cooper-pairs from the superconductor into the manganite, and the diffusion and transport of spin-polarized electrons from the manganite into the superconductor. The stacking sequence of the individual layers in these heterostructures was found to dictate the ground state properties of the heterostructure. Notably, the junction's behaviour was found to transform from superconducting to ferromagnetic with a simple alteration in the stacking order. These discoveries are set to drive advancements in spintronics and interfacial engineering, where controlling electronic properties through precise structural tuning of heterolayers is highly sought after. Additionally, the proximity effect has yielded a remarkable colossal-magnetoresistance (CMR) ratio of approximately 99%, establishing the heterostructure as a prospective candidate for technological applications.