Enhancement of the superconducting transition temperature by an external magnetic field parallel to the plane of La _0.7 Sr _0.3 MnO ₃ /YBa ₂ Cu ₃ O ₇ /La _0.7

Abstract

We investigate the superconducting transition temperature of epitaxial La0.7Sr0.3MnO3/YBa2Cu3O7/ La0.7Sr0.3MnO3 (LSMO/YBCO/LSMO) trilayers as a function of the magnetic field parallel to the layer structure. In these structures, the magnetic moment of the half-metallic ferromagnet LSMO is parallel to the plane of the film. The coercivity-and saturation field of the top and bottom LSMO layer could be independently tuned by adjusting their thickness. The application of a magnetic field increased the superconducting transition temperature by about 1.6 K with respect to the demagnetized state of the LSMO. Three possible mechanisms of the enhancement are considered. These are the stray fields due to domain walls, spin polarization of the current, and the formation of an odd triplet superconducting state.

Directionally controlled superconductivity in ferromagnet/superconductor/ferromagnet trilayers with biaxial easy axes

“…Due to different anisotropy fields, the rotations of M T and M B are dephased, resulting in a narrow plateau located between the coercive fields with a broadened base. 12,15,19 The largest MR is observed in this orientation. The shapes of the MR features do not depend on the direction of the excitation current with respect to the applied field, unlike for the AMR mechanism.…”

“…[12][13][14][15] The terms direct superconducting spin ͑DSS͒ and inverse superconducting spin ͑ISS͒ switch were introduced to describe enhanced or depressed superconductivity for AP alignment of the magnetizations of the ferromagnetic layers. 13 It has been accepted that an ISS governed by AP alignment ought to exhibit a well-defined positive plateau in the MR between the two coercive fields of top and bottom layers, 13,14,16 while a DSS governed by the exchange field effect would have a negative MR. 10 The domain state of the ferromagnet can also play a primary role in modulating the pairing amplitude by the ͑dipolar͒ stray fields generated by domains or domain walls 17 in a way which in F/S/F structures may also be determined by magnetic alignment.…”

Depth profile of the ferromagnetic order in a YBa2Cu3O7/LaUribe-Laverde1, Satapathy2, Marozau3 et al. 2013Phys. Rev. B

“…The common perovskite-related structure and similar in-plane lattice parameters, together with recent improvements in film deposition techniques, enable the layer by layer controlled epitaxial growth of multilayers and superlattices (SLs) with very sharp interfaces 17,20 . Experiments on this kind of oxide SC/FM heterostructures revealed effects such as a change in the SC critical temperature, T C , related to the presence and thickness of the FM layers, and vice-versa 17,19 ; a SC related giant magneto-resistance in FM/SC/FM trilayers 21 ; the enhancement of T C by an external magnetic field 22,23 and even a SC induced modulation of the magnetic moment in the FM layers 24 . These observations provide encouraging evidence for a sizable interaction between the SC and FM order parameters in these cuprate/manganite multilayer systems.…”

Localized Pair Breaking Effect in the Quasi-multilayers of YBa2Cu3O7−δ /La0.88Ca0.12MnO3

“…Recently, extensive research has been carried C. Chen ( ) · Y. Li · Y. Meng Physics Department, College of Science, Anhui University of Science and Technology, Huainan, 232001, China e-mail: czch68@163.com C. Cai Physics Department, Shanghai University, Shanghai 200444, China out on combinations of high-temperature superconductors (HTS) with colossal magnetoresistance (CMR) materials. Novel electronic states with distinct properties and functionalities can be generated at the interfaces of such perovskitetype oxide heterostructures, such as the decreased superconducting transition temperature T c in HTS/CMR multilayers (proximity effect) [3,4], the dependence of T c on the relative magnetization direction in CMR/HTS/CMR trilayers (spin valve effect) [5,6], as well as the suppressed critical current density induced by the spin injection effect in HTS/CMR bilayers [7,8]. Among these effects, one common feature is that the exchange field of the ferromagnet plays an important role in suppressing superconductivity.…”