In–Plane Rotational Magnetic Losses in a Laser Deposited YBa2Cu3O7−x Film

Abstract

One of the most remarkable features of the high-Tc superconducting materials is their large anisotropy of the crystal lattice and, consequently, of the superconducting properties, too. It was shown recently that torque magnetometry is a useful method for investigations of anisotropic magnetic properties of high-T superconducting single crystals 11, 21. Moreover, the method is also well suited for investigations of superconducting films as shall be demonstrated for the special case that the external field is slowly rotating in the film plane. In this way we tried to check the result of Roas et al. I31 who found in-plane isotropy of the critical current density j in contrast to the large j anisotropy perpendicular to the film plane.YBa2Cu307-x films on (100) SrTi03 substrates were prepared by laser ablation using an excimer laser. The deposition system is described elsewhere /4/. The films grow highly textured with the c-axes perpendicular to the mirror-like surface. For the X-ray rocking curve of the (005) film reflex we measured a width at half maximum of 0 . 7 5 ' .For torque measurements the film was carefully oriented with its plane, i.e. the CuO planes, parallel to the field-rotation plane (angle deviation < 0.15').Measurements were carried out in external fields of In order to estimate the pinning force acting on the vortices, we assumed a homogeneous distribution of defects and straight vortex lines. Then, the mean ) Helmholtzweg 4 , 0-6900 Jena, FRG . * ) Universitatsstr. 31, W-8400 Regensburg, FRG.