Superconducting levitation is an important application of superconductors. The levitation force between a permanent magnet and a superconductor is stable and requires no energy except for the system cooling. It is closely related to superconducting materials, permanent magnet and their geometrical dimensions. In this study, we investigate the influence of the thickness of MgB₂ bulks on their levitation and guidance forces. Three 50 mm diameter cylindrical samples were prepared by Spark Plasma Sintering – SPS [1] the thicknesses of which were 9mm, 4.9mm and 2.9mm, respectively. The 9mm thick disc was cut in two 4.5 mm parts. One of the parts was itself cut in two 2.2mm thick samples. The levitation and guidance forces of all the samples were measured at 20K with a system using a 70 mm diameter magnet. This type of measurement allows to determine the critical current density of the investigated superconductors and the thickness h of the layer carrying the superconducting currents [2]. The results have shown that the thickness of the samples has no significant effect on the levitation and guidance forces, but that h decreases with the sample thickness.

[1] Noudem J G, Xing Y, Bernstein P, Retoux R, Higuchi M, Arvapalli S S, Muralidhar M and Murakami M 2020 Improvement of critical current density of MgB2 bulk superconductor processed by Spark Plasma Sintering Journal of the American Ceramic Society 103 6169–75
[2] Bernstein P, Colson L, Dupont L and Noudem J 2017 Investigation of the levitation force of field-cooled YBCO and MgB2 disks as functions of temperature Superconductor Science and Technology 30 065007

Keywords: Bulk MgB2, Magnetic levitation force, Guidance force, Critical current density