Bc1 of high-Tc La1.8Sr0.2CuO4 and amorphous Zr70Cu30 superconductors measured by a vibrating reed

doi:10.1016/0375-9601(87)90350-1

Physics Letters A

Volume 123, Issue 9, 7 September 1987, Pages 485-488

https://doi.org/10.1016/0375-9601(87)90350-1 Get rights and content

Abstract

The lower critical field B_c1 of the high-T_c superconductor La_1.8Sr_0.2CuO₄ (T_c=40 K, B_c⩽7.7 mT) and of amorphous Zr₇₀Cu₃₀ (T_c=2.6K, B_c1⩽3.8 mT) is obtained from the resonance frequency ω/2π of a vibrating reed made of these materials. At applied magnetic fields B_a<B_c1, ω(B_a)=ω_i(B_a) as predicted for an ideally diamagnetic reed. Above B_c1 we observe a reversible linear law ω²−ω²_i∼B²_a−B²_c1. This allows a simple definition of B_c1 even in ceramic superconductors into which flux starts to penetrate at B_a⪡B_c1 due to their granular structure.

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¹: Instituto Balseiro, Universidad de Cuyo and CAB.

²: Member of the “Carreda del Investigador”, CONICET.

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Bc1 of high-Tc La1.8Sr0.2CuO4 and amorphous Zr70Cu30 superconductors measured by a vibrating reed

Abstract

J. Appl. Phys.

J. Appl. Phys.

Rev. Sci. Instrum.

Phys. Rev. Lett.

J. Low Temp. Phys.

J. Low Temp. Phys.

Phys. Lett. A

J. Magn. Magn. Mater.

B_c1 of high-T_c La_1.8Sr_0.2CuO₄ and amorphous Zr₇₀Cu₃₀ superconductors measured by a vibrating reed