Nondestructive inductive measurement of critical current densities in melt-textured YBa2Cu3O7 and SmBa2Cu3O7 using third-harmonic voltages

✍ Scribed by Hirofumi Yamasaki; Yasunori Mawatari; Yoshihiko Nakagawa

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 447 KB
• Volume: 405
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2004.02.005

✦ Synopsis

Local critical current densities J c of large melt-textured YBa 2 Cu 3 O 7 and SmBa 2 Cu 3 O 7 samples were nondestructively measured using a previously developed ac inductive technique [Appl. Phys. Lett. 83 (2003) 3972]. In this method an ac magnetic field is generated by an ac drive current (I 0 cos xt) in a small flat coil placed just above the superconductor, and a third-harmonic voltage (V 3 cos 3xt) generated in the same coil due to the nonlinear magnetic response of type-II superconductors is measured. Because V 3 is proportional to I 2 0 and inversely proportional to J c , J c can be measured in the surface region (typically down to $0.1 mm beneath the surface) of the bulk superconductor by measuring V 3 as a function of I 0 . The magnetic-field dependence of J c agreed reasonably well with that measured by using dc magnetization, if the effect of induced electric fields on J c is taken into account. By this ac inductive method J c can be measured by electric-field criteria (E c % 10 À4 -10 À2 V/m) that are higher than those generally used in transport measurements of J c (E c ¼ 10 À4 V/m). We can measure the distribution of J c in a large superconducting sample by scanning the measuring coil over the entire sample surface.