Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields

In this work we report the synthesis of RuSr 2 GdCu 2 O 8/ La 0.67 Sr 0.33 MnO 3 superconducting-magnetic composites with 50 vol.% of both RuSr 2 GdCu 2 O 8 and La 0.67 Sr 0.33 MnO 3 compounds. Structural characterization was performed by X-ray diffraction, which permitted us to establish the absence of other crystallographic phases and the non-reactive character of the compounds into the composite. Scanning electron microscopy showed the sub-micrometric size of the grains. Energy dispersive X-ray experiments confirmed chemical stability between RuSr 2 GdCu 2 O 8 and La 0.67 Sr 0.33 MnO 3 compounds in the composites. Resistivity measurements provided evidence of superconducting transition for the RuSr 2 GdCu 2 O 8 material, with TSC=39.2 K. Results of magnetization as a function of temperature corroborated the superconducting transition and showed the expected antiferromagnetic character of the Ru perovskite, with a Néel temperature TN=132.7 K. Systematic measurements of applied magnetic field up to 5 kOe were performed at these temperature regimes: TN < T < TC (with TC being the Curie temperature of the La 0.67 Sr 0.33 MnO 3 compound); TSC < T < TN; and T < TSC. Our results reveal the ferromagnetic character of the composites at the temperature regime TN < T < TC. The exchange bias effect was observed for weak applied fields (H < 1.5 kOe) at temperatures between TSC < T < TN. At the superconducting regime (T < TSC) weaker exchange bias is observed for low magnetic fields (H < 1 kOe). For strong magnetic fields (H > 2 kOe) the ferromagnetic character of the system is recovered.

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Resistance noise in high-Tc thin films at the superconducting transition in the presence of low magnetic fields

Physica C Superconductivity ◽

10.1016/0921-4534(94)91085-5 ◽

1994 ◽

Vol 235-240 ◽

pp. 3117-3118

Author(s):

C. Serrat ◽

A. Piqué ◽

J.M. Aponte

Keyword(s):

Thin Films ◽

Magnetic Fields ◽

Superconducting Transition ◽

High Tc ◽

Resistance Noise

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Superconductivity of tin isotopes

Mathematical Proceedings of the Cambridge Philosophical Society ◽

10.1017/s0305004100027250 ◽

1951 ◽

Vol 47 (4) ◽

pp. 811-819 ◽

Cited By ~ 57

Author(s):

J. M. Lock ◽

A. B. Pippard ◽

D. Shoenberg

Keyword(s):

Transition Temperature ◽

Magnetic Fields ◽

Specific Heat ◽

Critical Field ◽

Electronic Specific Heat ◽

Transition Temperatures ◽

Superconducting Transition ◽

Critical Magnetic Fields ◽

The Law

AbstractDetailed measurements have been made of the superconducting transition temperatures and critical magnetic fields of the tin isotopes of mass 116, 120 and 124. The transition temperature varies with isotopic mass according to the law Tc ∞ M−n, with n = 0·462 ± 0·014, a result very similar to that already found in mercury. The critical field curves of isotopes 116 and 124 are geometrically similar, in the sense that both many be represented by the same equation, Hc/Ho = f(T/Tc), with the same ratio Ho/Tc for both. It is deduced that the electronic specific heat in normal tin varies only slowly, if at all, with isotopic mass. The variation of Tc and Ho with M is very close to that predicted by Fröhlich and Bardeen.

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