Magnetic Penetration Depth and Coherence Length in a Single‐Crystal YBa2Cu3O7−δ

Abstract

Herein, DC magnetization measurements of high‐quality single crystals of optimally doped YBa2Cu3O7−δ(YBCO) superconductor are reported on. The temperature and orientation dependence of the magnetic penetration depth for single‐crystal YBCO is estimated from the slope of the linear M(lnH) dependence in the London regime. The penetration depth is strongly anisotropic. Also, the electrical resistivity as a function of temperature in YBCO thin film deposited by laser ablation on the SrTiO3 substrate face is investigated around the superconducting transition region under various values of the magnetic field up to 14 T. In this work, based on the resistivity measurements, the upper critical magnetic field for both directions B∥c‐axis and B⊥c‐axis is determined with a DC weak transport current density by using 90% criteria of the normal‐state resistivity value. According to the relations and , the coherence length (0) and (0) is determined, where is the magnetic flux quantum. The anisotropy parameter is calculated and analyzed within the frame of Ginzburg–Landau theory. This result indicates that anisotropy is more evident in YBCO.