Possible origin for the T2 dependence of the penetration depth detected by susceptibility measurements in aligned YBa2Cu3O7 powder samples

✍ Scribed by L. Guerrin; H. Alloul; G. Collin

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 908 KB
• Volume: 251
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(95)00419-x

✦ Synopsis

Accurate measurements of the AC susceptibility x(T) have been performed on oriented YBa2Cu307 powder samples of various calibrated sizes at nearly perfect 0 7 oxygen stoichiometry with an AC magnetic field applied either perpendicular or parallel to the ab plane. The changes in x(T) with the average crystallite size and with the field direction are analyzed. The temperature variations of x(T) directly reflect those of A(T) and in both directions a quadratic temperature dependence is found for T < 0.2T c. This result differs markedly from those obtained by surface impedance measurements on single crystals by Hardy et al. and is inconsistent with a BCS model with an isotropic superconducting gap. The variations of X(4.2 K) as a function of the grain size suggest that the penetration depth actually measured is dominated by A c in both directions. The difference between the microwave and susceptibility data might then be associated with differences in the temperature dependence of hab and h c.