An experimental study on decay characteristics of magnetized flux in YBCO-QMG bulk material under AC magnetic field

We have examined the decay characteristics of magnetized flux in a YBCO-QMG bulk material in a weak AC magnetic field with a magnitude around the lower critical magnetic field. The frequency of the applied magnetic field is 50 Hz. The magnetic field is applied in two directions that are parallel and perpendicular to the direction of the original magnetization field which corresponds to the C-axis of the YBCO bulk. The measurements of the magnetized flux decay are performed for one hour. The experimental result shows that the decay of the magnetic flux depends greatly on the direction of the applied external AC magnetic field. According to our experiment, the decay of the magnetized flux for the perpendicular direction AC magnetic field is about two times larger to that for the parallel direction.