Magnetism and superconductivity in La0.7Ca0.3MnO3/YBa2Cu3O7−δ superlattices (original) (raw)
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Journal of Applied Physics, 2001
We report on the magnetic and superconducting properties of La 0.7 Ca 0.3 MnO 3 /YBa 2 Cu 3 O 7 ͑LCMO/ YBCO͒ superlattices. For a constant LCMO layer thickness of 6 unit cells ͑u.c.͒, resistance and susceptibility measurements show superconductivity for YBCO layer thickness in excess of 4 unit cells. The critical temperature increases with YBCO thickness, and a T c of 58 K is found for a YBCO thickness of 10 unit cells. Magnetization measurements show a ferromagnetic transition at 100 K in a (LCMO 6 u.c. /YBCO 5 u.c. ͒ 15 bilayer superlattice, and a depressed value of the saturation magnetization of 20 emu cm Ϫ3 . These results are discussed in terms of interface disorder ͑analyzed by x-ray diffraction and transmission electron microscopy͒ and of the possible interaction between magnetism and superconductivity.
2002
We report on the depression of the superconducting critical temperature of ultra thin YBa2Cu3O7 (YBCO) layers, when their thickness is reduced in presence of La0.7Ca0.3MnO3 (LCMO) magnetic layers in [LCMO (15 u.c.)/ YBCO(N u.c.)] superlattices. The thickness of the manganite layer is kept at 15 unit cells and the YBCO thickness is varied between N=12 and N=1 unit cells. The structural analysis using x-ray diffraction and electron microscopy shows sharp interfaces with little structural disorder. While a critical temperature, Tc=85 K is found for 12 YBCO unit cells, superconductivity is completely suppressed for YBCO layer thickness below 3 unit cells. The possible interaction between superconductivity and magnetism is investigated.
Ferromagnetic/superconducting proximity effect in La0.7Ca0.3MnO3/YBa2Cu3O7-δ superlattices
Physical Review B, 2003
We study the interplay between magnetism and superconductivity in high quality YBa 2 Cu 3 O 7 (YBCO) / La 0.7 Ca 0.3 MnO 3 (LCMO) superlattices. We find evidence for the YBCO superconductivity depression in presence of the LCMO layers. We show that due to its short coherence length superconductivity survives in the YBCO down to much smaller thickness in presence of the magnetic layer than in low Tc superconductors. We also find that for a fixed thickness of the superconducting layer, superconductivity is depressed over a thickness interval of the magnetic layer in the 100 nm range. This is a much longer length scale than that predicted by the theory of ferromagnetic/superconducting proximity effect.
Magnetic properties of La0.67Sr0.33MnO3/YBa2Cu3O7 superlattices
Physical Review B, 2004
Oxide multilayers composed of ferromagnetic metallic layers of La 0.67 Sr 0.33 MnO 3 ͑LSMO͒ and superconducting cuprate YBa 2 Cu 3 O 7 ͑YBCO͒ were grown on ͑1 0 0͒ LaAlO 3 substrates by high-pressure dc sputtering. We have investigated structural, transport, and magnetic properties of a series of samples in which the layer thickness of LSMO is fixed at 16 unit cells and that of YBCO varied from 1 to 8 unit cells. Exchange-induced unidirectional anisotropy in LSMO/YBCO superlattices has been demonstrated. Observation of an exchange biasing effect in LSMO/YBCO superlattices supports an existence of interlayer exchange coupling between LSMO layers through YBCO superconducting spacer layers.
Superconductivity and Ferromagnetism in La0.67Sr0.33MnO3/YBa2Cu3O7Nanosized Heterostructures
Acta Physica Polonica A, 2016
In this work we present recent experimental studies of heterostructures composed of ferromagnetic La0.67Sr0.33MnO3 (LSMO) and superconducting YBa2Cu3O7 (YBCO) multilayers grown by dc sputtering method. The transport and magnetic properties of the large set of heterostructures were investigated in a wide temperature range from 2 to 400 K and in fields up to 12.5 T. The resistivity and the upper critical field were measured for samples with the plane active dimensions 1.5×5 mm 2. The Nernst effect was studied in the mixed state revealing the characteristic temperature dependence of the Nernst signal which was correlated with variation of the upper critical field. We have observed an influence of the magnetic LSMO layer on the superconducting properties of the adjacent YBCO layer which consists in a substantial reduction of the superconducting critical temperature and a small lowering of the upper critical field.
Activation energy in La0.7Ca0.3MnO3/YBa2Cu3O7-δ / La0.7Ca0.3MnO3 superconducting trilayers
The European Physical Journal B, 2006
Resistivity vs. temperature measurements on La0.7Ca0.3MnO3/YBa2Cu3O 7−δ /La0.7Ca0.3MnO3 (LCMO/YBCO/LCMO) trilayers with different YBCO thickness, were performed in external magnetic field H up to 8 T. By evaluating the activation energy U from the slope of the resistivity Arrhenius plot, a strong depression of U has been observed when decreasing the YBCO layer thickness and the absolute U values appear to be reduced with respect to the values reported in literature in the case of YBCO thin films and YBCO/insulating multilayers. Moreover, a logarithmic U vs. H dependence is shown both in the case of thick and thin YBCO layers indicating the formation of a two dimensional vortex lattice. The experimental data are discussed considering the strong influence of the ferromagnetic LCMO on the superconducting YBCO properties which reduces the effective YBCO thickness more than predicted by the conventional theories.