Welpet al. reply

Abstract

Welp et al. Reply:We do not agree with Salamon and Shi's (SS) suggestions [1] that our high-field scaling [2] of the magnetization of YBa2Cu307-5 crystals near the diamagnetic transition is inadequate, for the following reasons.SS argue that the LLL approximation [3] is not applicable to most of our data. Equation (3) of the Comment, however, is only a qualitative argument for the crossover between two regimes (LLL-next LL) but not a welldefined cutoff. For quasi-2D superconductors in perpendicular fields the crossover has been estimated to occur near HdiT)/![4] which translates into \T-TC{H)\

Scaling behavior of conductivity and magnetization in high-temperature superconductors

“…Indeed, a similar feature has already been encountered for YBa 2 Cu 3 O 7 by Welp et al 5 and Wilkin et al 19 For this compound, these authors could hardly determine the more appro- priate scaling form, the two plots being very similar. Nevertheless, they have finally estimated that the threedimensional mode is more satisfactory near the transition while, at higher temperatures, YBa 2 Cu 3 O 7 cannot be accurately treated as a continuum and the vestiges of its microscopic layered structure has to be considered by using the 2D form.…”

“…Usually, the analysis of the fluctuations is carried out through scaling laws because of the lack of any general expression applicable in both the pure threedimensional ͑3D͒ or two-dimensional ͑2D͒ case for the whole temperature range. Recently, on the basis of this scaling approach, numerous experimental papers [1][2][3][4][5] have succeeded in discussing the phenomenon of the critical fluctuations in terms of the lowest Landau level ͑LLL͒ approximation, 6,7 which holds in a region of the phase diagram close to a renormalized H C 2 (T). The relevance of a scaling behavior exhibited by physical properties within this approximation has been presented for many types of HTSC's.…”

“…The relevance of a scaling behavior exhibited by physical properties within this approximation has been presented for many types of HTSC's. 8,4,5 Through such an analysis it is then possible to study the influence of the dimensionality effects on the fluctuations. These dimensionality effects are directly related to the degree of anisotropy of the system which increases from YBa 2 Cu 3 O 7 to thallium-based compounds such as Tl 2 Ba 2 CaCu 2 O 8 ͑Tl-2212͒.…”

Elastic study of antiferromagnetic fluctuations in the layered organic superconductorsκ−(BEDT−TTF)2X

“…Indeed, at ambient pressure, the compounds with X = Cu[N(CN) 2 ]Br and Cu(SCN) 2 are showing superconducting ground states around 10 K, while an insulating one with antiferromagnetic ordering is obtained below 25 K for X = Cu[N(CN) 2 ]Cl. [3][4][5] However, the latter compound shows also a superconducting ground state around 12 K under a small hydrostatic pressure of 300 bar. 6 In view of the strong dimerization of the BEDT-TTF molecules, this pressure induced metal-insulator transition results from the competition between the repulsive Coulomb energy (U) and the bandwidth (W) in the effectively halffilled electronic band structure (Mott transition).…”

Equilibrium magnetization of aBi2Sr2Martı́nez1, Linden2, Bulaevskiǐ3 et al. 1994Phys. Rev. Lett.

“…At high temperatures and close to T,p (T ) 70 K) we are in the classical region and the data must be fitted by Eq. (2). The temperature where the magnetization is field independent is T' = 84.3 + 0.9 K. At T' we obtain for our sample Ms(T = T') = 0.3 mT.…”