Relaxation behaviour of levitation forces of various thin high-Tc superconductor samples

We present the construction of a so-called levitation balance which is capable of measuring the levitation forces between a permanent magnet and a superconducting high-Tc thin film sample. Using this setup, we measure the relaxation behaviour of the levitation forces of different thin high-Tc samples: YBCO thin films as well as a commercial YBCO coated conductor and a piece of an Ag-sheathed Bi-2223 tape. From the relaxation curves, we obtain the pinning energies, which correspond well to the data of conventional relaxation measurements. We further show that a small movement of the sample prior to the relaxation measurement influences the relaxation behaviour drastically, so a situation with practically no relaxation effects can be generated.