Field-cooled magnetization measurements of Nd-123 bulk superconductors

The field-cooled (FC) magnetization M is measured as a function of the appl ied external field, H-a, for various bulk, Nd-based 123 superconductors whi ch exhibit different magnetization-field characteristics (i.e. with and wit hout secondary peak effect). We find that the FC magnetization data reprodu ce directly the M(H-a) behaviour measured after zero-field cooling. Based o n the critical state model, we derive expressions for the field-cooled magn etization, and show that a large M(0) is essential to achieve large trapped fields in superconducting permanent magnets.