Field Dependence of Critical Current of YBa₂Cu₃O_7-Film in Low Magnetic Field

Two components of critical current in YBa$_2$Cu$_3$O$_{7-δ}$ films

“…For small b it follows a power law and in the range 10 −4 ≤ b ≤ 0.005 is approximated as f = 0.5552 • b −0.537 with the accuracy of ±1.2%. The dependence J ∝ B −α with α 0.4-0.8 was often observed for YBa 2 Cu 3 O 7−δ films 10,12,19,21,23,52,64 and 2G-tapes. 9 As seen in Fig.…”

“…Due to strong demagnetization effect a self demagnetizing field is produced by current flowing in a superconducting film when field is applied perpendicular to the film plane. [50][51][52] In the critical state this self field exists even after complete removal of external field. The measurements were performed for applied fields of 910 and 1530 Oe and in self-field after removing field of 2090 Oe.…”

“…Combining M * with data on δM (t) we precisely obtained the time dependence of the magnetic moment M (t). 52,57 Examples of M (t) curves obtained at low and high temperatures are shown in Figure 1. As seen, the noise of the curves is considerably lower than the change of the moment due to relaxation.…”

“…Preliminary results of the relaxation experiments were published elsewhere. 52,57,58 In the present work we analyze the current obtained from the M * (T ) dependences so let us consider this issue in detail.…”