Ubiquitous long-range antiferromagnetic coupling across the interface between superconducting and ferromagnetic oxides

Abstract

The so-called proximity effect is the manifestation, across an interface, of the systematic competition between magnetic order and superconductivity. This phenomenon has been well documented and understood for conventional superconductors coupled with metallic ferromagnets; however it is still less known for oxide materials, where much higher critical temperatures are offered by copper oxide-based superconductors. Here we show that, even in the absence of direct Cu-O-Mn covalent bonding, the interfacial CuO 2 planes of superconducting La 1.85 Sr 0.15 CuO 4 thin films develop weak ferromagnetism associated to the charge transfer of spin-polarised electrons from the La 0.66 Sr 0.33 MnO 3 ferromagnet. Theoretical modelling confirms that this effect is general to all cuprate/manganite heterostructures and the presence of direct bonding only affects the strength of the coupling. The DzyaloshinskiiMoriya interaction, also at the origin of the weak ferromagnetism of bulk cuprates, propagates the magnetisation from the interface CuO 2 planes into the superconductor, eventually depressing its critical temperature.

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

“…The XMCD signal at 100 K (Fig. 5(f)) is ambiguous for S2 and can be interpreted as unclear magnetism, similar to that reported earlier in a similar system 21 . It was reported that at 100 K, there was no Cu magnetic moment for a 25 u.c.…”

X-ray absorption study of the ferromagnetic Cu moment at theYBa2Cu3O7/La2/3Ca1Sen1, Perret2, Alberca3 et al. 2016Phys. Rev. B213260View full textAdd to dashboardCite

“…The second possibility, where the paramagnetic Cu XCMD originates from bulklike Cu ions, was suggested in Ref. [36], which reported similar XMCD data for corresponding LSCO/LCMO MLs. Nevertheless, as shown in the following, we can exclude such a two-component scenario for the case of these YBCO/LCMO MLs.…”

“…An additional argument against the two-component scenario of Ref. [36] is that such a paramagnetic signal is not observed in YL 1, despite the circumstance that this sample contains the same amount of bulklike Cu ions as YL 2.…”

Atomic-resolution studies of epitaxial strain release mechanisms inLa1.85Sr0.15CuO4Biškup1, Das2, Gonzalez-Calbet3 et al. 2015Phys. Rev. B4030View full textAdd to dashboardCite

“…Such systems allow the study of antagonistic superconducting and ferromagnetic order parameters, giving rise to exotic behaviors. A prominent example of a resulting effect can be found in the magnetic proximity effect which gives rise to a strong suppression of the FM moment of the Mn ions on the manganite side of the interface and yet a small induced FM moment of the Cu ions (that is antiparallel to the one of Mn) on the cuprate side [10][11][12][13][14][15][16][17]. The systems that are studied in most cases are superlattices (SLs) combining the cuprate YBa 2 Cu 3 O 7−x and the manganite La 1−x (Sr,Ca) x MnO 3 since the similarity of their lattice constants results in sharp and coherent epitaxial interfaces [12,18].…”