Temperature-dependent critical currents in superconducting YBa2Cu3O7−δ and ferromagnetic La2/3Ca1/3MnO3 hybrid structures

Abstract

The local critical current density in thin-film hybrid structures of high-temperature superconducting YBa2Cu3O7−δ and ferromagnetic La2/3Ca1/3MnO3 (LCMO) is measured with high accuracy using a quantitative magneto-optical method. The superconducting films are grown onto vicinal cut substrates where step-flow growth creates a highly ordered microstructure including an array of parallel oriented planar defects. This generates an anisotropy of the critical current in the superconductor, arising from the different values of the current density depending on whether it has to flow across the defects or not. The addition of an LCMO layer leads to an increase of the current anisotropy meaning that the two nonequivalent current directions are affected by the stray field of the adjacent ferromagnet in different ways. The magnetization of the ferromagnetic LCMO is mainly in-plane oriented but exhibits finite out-of-plane components originated from a high density of Néel-type domain walls. Performing temperature-dependent measurements of the critical current density from T=7 K to T=90 K and comparing with results from YBCO single layers, the influence of the ferromagnet on the critical current density is studied in detail. It is found that depending on the defect structure of the current path the critical currents are affected in different ways by the ferromagnet. The comparison of single layer superconducting films and heterostructures in conjunction with the realized different microstructure along the current path inside one individual sample, allows the identification of the current transport mechanisms in YBCO thin films and how they are influenced by the magnetic stray fields from the added LCMO layer.

Source-reported materials — not catalogue approval

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