Trapped magnetic field distribution above two magnetized bulk superconductors close to each other

Bulk large-grain superconductors can be used as high-field permanent magnets. Although the
properties of such individual trapped field magnets are well documented, much less is known
concerning their behaviour when two are brought together. In this work, the interaction between
two cylindrical bulk YBa2Cu3O7 (YBCO) superconductors is described. Two sets of
experiments were carried out. The first involved the simultaneous magnetization of two bulk
superconductors placed a short distance apart. Here, the applied magnetic field was aligned
parallel to the c-axis of one bulk, while the other was oriented with its c-axis offset . For a
centre-to-centre distance equal to twice the sample height, the presence of the second sample is
found not to alter the current distribution inside the first. Consequently, the contribution of both
samples simply sums, thus increasing the magnetic flux density between them. In the second set
of experiments, the translational approach of the superconductors with parallel c-axes was
investigated. The following configurations were considered: (i) face to face approach (with
anti-parallel trapped field orientation) and (ii) sideways approach (with parallel trapped field
orientation). An irreversible decrease of the trapped field was measured on separation . Repeated
approach cycles showed that the irreversible loss of trapped field is largest for the first approach.