Selective interlayer ferromagnetic coupling between the Cu spins in YBa$_2$ Cu$_3$ O$_{7-x}$ grown on top of La$_{0.7}$ Ca$_{0.3}$ MnO$_3$

S. W. Huang; L. Andrew Wray; Horng-Tay Jeng; V. T. Tra; J. M. Lee; M. C. Langner; J. M. Chen; S. Roy; Y. H. Chu; R. W. Schoenlein; Y. -D. Chuang; J. -Y Lin

doi:10.1038/srep16690

arXiv · 1504.01820

Selective interlayer ferromagnetic coupling between the Cu spins in YBa$_2$ Cu$_3$ O$_{7-x}$ grown on top of La$_{0.7}$ Ca$_{0.3}$ MnO$_3$

S. W. Huang·L. Andrew Wray·Horng-Tay Jeng·V. T. Tra·J. M. Lee·M. C. Langner·J. M. Chen·S. Roy·Y. H. Chu·R. W. Schoenlein·Y. -D. Chuang·J. -Y Lin

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Abstract

Studies to date on ferromagnet/d-wave superconductor heterostructures focus mainly on the effects at or near the interfaces while the response of bulk properties to heterostructuring is overlooked. Here we use resonant soft x-ray scattering spectroscopy to reveal a novel c-axis ferromagnetic coupling between the in-plane Cu spins in YBa$_2$ Cu$_3$ O$_{7-x}$ (YBCO) superconductor when it is grown on top of ferromagnetic La$_{0.7}$ Ca$_{0.3}$ MnO$_3$ (LCMO) manganite layer. This coupling, present in both normal and superconducting states of YBCO, is sensitive to the interfacial termination such that it is only observed in bilayers with MnO_2but not with La$_{0.7}$ Ca$_{0.3}$ interfacial termination. Such contrasting behaviors, we propose, are due to distinct energetic of CuO chain and CuO$_2$ plane at the La$_{0.7}$ Ca$_{0.3}$ and MnO$_2$ terminated interfaces respectively, therefore influencing the transfer of spin-polarized electrons from manganite to cuprate differently. Our findings suggest that the superconducting/ferromagnetic bilayers with proper interfacial engineering can be good candidates for searching the theorized Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state in cuprates and studying the competing quantum orders in highly correlated electron systems.

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S. W. Huang, L. Andrew Wray, Horng-Tay Jeng, V. T. Tra, J. M. Lee, M. C. Langner, J. M. Chen, S. Roy, Y. H. Chu, R. W. Schoenlein, Y. -D. Chuang, J. -Y Lin. 2015-04-08. Selective interlayer ferromagnetic coupling between the Cu spins in YBa$_2$ Cu$_3$ O$_{7-x}$ grown on top of La$_{0.7}$ Ca$_{0.3}$ MnO$_3$. https://doi.org/10.1038/srep16690

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