Anisotropic effects in a powder oriented YBCO sample using a three axes magnetometer

摘要

To measure the components of the magnetization vector along the XYZ directions of a reference frame, in the superconducting materials, we have conceived a three axes magnetometer, with a detection system equipped with three series of pick-up coils with axes parallel to the three directions X,Y, and Z. We describe in this paper the details of the design and the method of measurement, with some results obtained by magnetic measurements on samples of oriented YBCO powder, with size of the grains between 20 μm and 40 μm, for values of the angle θ between the magnetic field H and the c-axis, between 0° and 90° and for values of fields up to 12 T. The direct measurement of the Z and the XY components of the irreversible magnetization vector, M_(irr), allowed us to observe the twin effect (channeling) on the vortex pinning observed by many authors, the evolution of the magnetization vector and to measure with a high accuracy the anisotropy factor of our samples.