The intercomparison covers the determination of :
- remanent induction Br;
- coercivities HcB and HcJ;
- maximum energy product (HB)max.
NdFeB and AlNiCo8 have been selected because of their properties and technological importance.
Two classes of measuring techniques will be used by the participants. The first and most widely used employs a closed circuit apparatus, in which cylindrical samples are placed in between the poles of an electromagnet. In the second, approximately 3 mm diameter spheres will be held in the field of an open circuit apparatus, such as vibrating magnetometers. This latter intercomparison will be limited to NdFeB, because, in this configuration, the high remanence and low coercivity of AlNiCo8 make it difficult to correct for demagnetizing effects.
As accurate calibration is an essential prerequisite for the success of the intercomparison, reference samples will be distributed to all participants.
Besides AlNiCO and NdFeB specimens, Ni reference specimens were also circulated for calibration purposes. The results of the audits are complex, but in general it can be said that the agreement obtained has been quite good within the two separate groups (cylinders and spheres). The correlation between the results of the two separate methods turned out to be unsatisfactory in so far as the small spherical specimens had changed their properties as a results of the preparation process.
Funding SchemeCSC - Cost-sharing contracts
20123 Caronno Pertusella
21023 Malgesso Varese
TW11 0LW Teddington