Lower critical field, temperature dependence

In Fig. 3 we have plotted the temperature dependence of the upper and lower critical fields, determined as described earlier. For the upper critical field we observe that, except in the vicinity of the critical temperature... 

The temperature dependence of the lower critical field follows within a few percent the empirical law [8]... 

FIG. 3. (a) The temperature dependence of the lower critical field //, ifT) determined on a powder sample as shown in the inset and explained in the text. Error bars represent estimated uncertainty in determining H . The solid line represents the empirical law //, i(7 )/W, i(0) 1 —(T/T, ). (b) The temperature dependence of the upper critical field H, i(T). Inset The method of determining these values from M(T) curves at fixed field. The error bars in the main plot reflect the round-... 

We have analyzed the thermodynamic, magnetic and ultrasound attenuation data on oriented saaiples of the hlgh-T superconductors within the context of anisotropic Glnzburg-LSndau theory for coupled, even-parity superconducting states. We are able to present a consistent Interpretation of the data In terms of the coexistence of a quasi-two-dimensional d-wave state, with critical temperature T. - T and a more Isotropic mixed (s+d)-wave state with critical tempertaure T < T We predict the possibility of a "kink" in the temperature dependence of the lower critical field near 0 9T, which should be tested by experiments on single crystals. 

S. Riedling, J. Franz, T. Ishida, A. Erb, G. Muller-Vogt, H. Wiihl Phase separation in YBa2Cu307 5 single crystals near 5 = 0, Physica C 200, 271-276 (1992) D.-H. Wu, S. Sridhar Pinning forces and lower critical fields in YBa2Cu30y crystals Temperature dependence and anisotropy, Phys. Rev. Lett. 65, 2074-2077 (1990)... 

We have measured the temperature dependence of the lower and upper critical fields in superconducting KjCso. From the measurements, we have evaluated the jwnetration depth (X 2400 A) and superconducting coherence length ( 26 A). The parameters are in agreement with a superconducting state formed by a narrow band. 

Fields of applicability. Figure 15.3 depicts the fields of applicability of pickled stainless steels in chloride-contaminated concrete exposed to temperatures of 20 °C or 40 °C. Fields have been plotted by analysing the critical chloride values obtained by different authors from exposure tests in concrete or from electrochemical tests in solution and mortar and taking into consideration the worst conditions [11-28]. Nevertheless, it should be pointed out that values are indicative only, since the critical chloride content depends on the potential of the steel, and thus it can vary when oxygen access to the reinforcement is restricted as well as when stray current or macrocells are present. For instance, the domains of applicability are enlarged when the free corrosion potential is reduced, such as in saturated concrete. Furthermore, the values of the critical chloride Hmit for stainless steel with surface finishing other than that obtained by pickling can be lower. 

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