Magneto-transport in La_2/3Sr_1/3MnO₃/YBa₂Cu₃O₇/Alq₃/Co spin-valves

¹ Physics Department and Fribourg Center for Nanomaterials (FriMat), University of Fribourg - Chemin du Musée 3, CH-1700 Fribourg, Switzerland
² CSEM SA - Rue Jaquet-Droz 1, CH-2002 Neuchâtel, Switzerland
³ Institute for Solid State Physics, Karlsruhe Institute of Technology - D-76344 Eggenstein- Leopoldshafen, Germany
⁴ Department of Physics, Stockholm University, AlbaNova University Center - SE-10691 Stockholm, Sweden

^(a) andrea.cerreta@outlook.com
^(b) christian.bernhard@unifr.ch

Received: 13 December 2019
Accepted: 7 February 2020

Abstract

We studied how an additional layer of the high superconductor YBCO affects the magneto-transport across a LSMO/Alq₃/Co spin-valve structure. We found that up to a thickness of at least 10 nm the YBCO layer on top of LSMO hardly changes the spin-valve effect, since the device resistance still depends on the relative orientation of the LSMO and Co magnetization. The spin-valve effect persists even when the superconducting YBCO layer acts as bottom electrode, with no spin-polarized current injected from LSMO into YBCO. This highlights that the charge carriers of a thin YBCO layer on top of LSMO are strongly spin-polarized, most likely due to a magnetic proximity effect involving a transfer of spin-polarized electrons from LSMO to YBCO. Evidence for a strongly underdoped state of the YBCO layers close to the interface with LSMO is indeed obtained from the dI/dV curves in zero magnetic field which reveal a pseudogap persisting well above .