Proximity effects across oxide-interfaces of superconductor-insulator-ferromagnet hybrid heterostructure

Abstract

A case study of electron tunneling or charge-transfer-driven orbital ordering in superconductor (SC)-ferromagnet (FM) interfaces has been conducted in heteroepitaxial YBa2Cu3O7(YBCO)/La0.67Sr0.33MnO3(LSMO) multilayers interleaved with and without an insulating SrTiO3(STO) layer between YBCO and LSMO. X-ray magnetic circular dichroism experiments revealed anti-parallel alignment of Mn magnetic moments and induced Cu magnetic moments in a YBCO/LSMO multilayer. As compared to an isolated LSMO layer, the YBCO/LSMO multilayer displayed a (50%) weaker Mn magnetic signal, which is related to the usual proximity effect. It was a surprise that a similar proximity effect was also observed in a YBCO/STO/LSMO multilayer, however, the Mn signal was reduced by 20%. This reduced magnetic moment of Mn was further verified by depth sensitive polarized neutron reflectivity. Electron energy loss spectroscopy experiment showed the evidence of Ti magnetic polarization at the interfaces of the YBCO/STO/LSMO multilayer. This crossover magnetization is due to a transfer of interface electrons that migrate from Ti(4+)−δ to Mn at the STO/LSMO interface and to Cu2+ at the STO/YBCO interface, with hybridization via O 2p orbitals. So charge-transfer driven orbital ordering is the mechanism responsible for the observed proximity effect and Mn-Cu anti-parallel coupling in YBCO/STO/LSMO. This work provides an effective pathway in understanding the aspect of long range proximity effect and consequent orbital degeneracy parameter in magnetic coupling.

Ferromagnetism and Superconductivity in CaRuO3/YBa2Cu3O7-δ Heterostructures

“…After the deposition of the CRO layer, for all samples was observed the same value of compressive strain for the b lattice constant of the YBCO layer and a tensile strain in the case of a and c lattice constants. Moreover, the T c of YBCO is smaller in these samples regardless of the presence of the STO interlayer, which may imply a modification in stoichiometry leading to an under-doped YBCO [ 62 , 63 ]. Differences observed in the strain of the YBCO layer and temperature-dependent magnetic moment curves from Figure 2 b of samples II-a, II-b, III-a, and III-b, respectively, may be partly caused by a change in the site of apical oxygen [ 55 ].…”

Embedded Magnetism in YBa2Cu3O7 Associated with Cu–O Vacancies within Nanoscale Intergrowths: Implications for Superconducting Current Performance

“…Researchers investigating the magnetic properties of superconducting/ferromagnetic heterostructures should be aware of this result, as the presence of these type of complex-vacancies at interfaces, even in very well controlled growth conditions, often occurs. [33][34][35][36][37] Angular dependence. In order to gain insight into the anisotropic characteristics of the defectdriven moments, we performed XAS & XMCD measurements as a function of the beam incident angle, in TEY mode.…”

Complementary Insights from Neutron and Resonant X‐Ray Reflectometry for the Study of Perovskite Transition Metal Oxide Heterostructures

“…These requirements are met at several instruments around the globe, where it is possible to perform NR of oxide heterostructures. Some recent examples come from studies carried out at large-scale facilities such as FRM II, [35][36][37] ILL, [38] SINQ, [39] ISIS, [40] SNS, [41,42] and NIST. [43][44][45] To demonstrate this important, complementary aspect of Xrays and neutrons, we show simulations for a hypothetical SrVO 3 =SrCrO 3 SL structure in Figure 2.…”

“…These requirements are met at several instruments around the globe, where it is possible to perform NR of oxide heterostructures. Some recent examples come from studies carried out at large‐scale facilities such as FRM II, [ 35–37 ] ILL, [ 38 ] SINQ, [ 39 ] ISIS, [ 40 ] SNS, [ 41,42 ] and NIST. [ 43–45 ]…”