Measurements of the absolute value of the penetration depth in high-Tc superconductors using a low-Tc superconductive coating

Abstract

A method is presented to measure the absolute value of the London penetration depth, λ(T=0), from the frequency shift of a resonator. The technique involves coating a high-Tc superconductor with film of low-Tc material of known thickness and penetration depth. The method is applied to obtain λ(YBa2Cu3O7−δ)≈1460±150 Å, λ(Bi2Sr2CaCu2O8+δ)≈2690±150 Å and λ(Pr1.85Ce0.15CuO4−δ)≈2790±150 Å. λ(YBa2Cu3O7−δ) from this method is very close to that obtained by several other techniques. For both Bi2Sr2CaCu2O8+δ and Pr1.85Ce0.15CuO4−δ the values exceed those obtained by other methods.

Magnetic penetration depth in unconventional superconductors

“…We will touch briefly upon some of these methods, but will restrict most examples in this paper to data taken using a tunnel diode oscillator technique developed over the past several years at the University of Illinois. [46,47,168,169] This is essentially a cavity perturbation technique, albeit at rf frequencies. In the microwave approach [88, Jacobs, 1995#218, Mao, 1995 a very high quality factor cavity is typically driven externally while its in-phase and quadrature response are measured.…”

“…The sample under study is coated with a lower-T c material (typically Al) of known thickness and penetration depth. [84,169] If the film thickness is smaller than its normal state skin depth, then above ( ) …”

Nodal superconductivity in isovalently substituted SrFe2(As1−xPxMurphy1, Strehlow2, Cho3 et al. 2013Phys. Rev. BSelf Cite239160View full textAdd to dashboardCite

“…Knowing the variation of ∆λ(T ), the superfluid density is given by ρ s (T ) = λ 2 (0)/λ 2 (T ) = (1 + ∆λ(T )/λ(0)) −2 , so we need to know the absolute value of zero -temperature penetration depth, λ(0). To obtain this value we used TDR measurements of Al coated samples [44]. After initial measurement of ∆λ(T ) each sample is uniformly coated with Al using magnetron sputtering and then remeasured [44,45].…”

“…To obtain this value we used TDR measurements of Al coated samples [44]. After initial measurement of ∆λ(T ) each sample is uniformly coated with Al using magnetron sputtering and then remeasured [44,45]. To ensure a uniform Al film thickness the sample is suspended by a fine wire from a rotating stage inside the sputter deposition chamber.…”

Campbell penetration depth of a superconductor in the critical state

“…With λ L (0) ≈ 2690Å, determined from our earlier measurements [17] we obtain total penetration depth λ C (B, T, j). Fig.…”