A NEW CALIBRATION TECHNIQUE FOR THE DETERMINATION OF MAGNETIC-FLUX DENSITY WITH THE MAGNETOOPTICAL FARADAY-EFFECT

Using the high resolution magneto-optical Faraday effect the magnetic flux density distribution of circular shaped Y1Ba2Cu3O7-x thin films is investigated. A new calibration technique is developed to determine the z-component B(z)(x,y) of the local magnetic flux density B(x,y) in the x,y-surface of the films with high accuracy. The observed flux density profiles agree well with calculations of B(r) using a simple model with homogeneous current distribution. The appearance of a negative magnetic flux and reversed flux lines at the edge of the films in the remanent state is caused by stray fields of the trapped flux. For a determination of the local critical current density j(C), the local pinning forces p(V) and the magnetization of thin films from the observed magnetic flux density distribution B(x,y) the curvature of the magnetic field partial derivative B(z)/partial derivative r and partial derivative B(r)/partial derivative z, respectively, has to be taken into account.