CHARACTERIZATION OF PERMANENT MAGNETS WITH THE PULSED FIELD MAGNETIZER

• Published in: Journal of Optoelectronics and Advanced Materials Vol. 6; no. 3; pp. 963 - 968
• Main Authors: Beatrice, C, Bottauscio, O, Ferrara, E, Fiorillo, F, Patroi, E
• Format: Journal Article
• Language: English
• Published: 01.09.2004
• ISSN: 1454-4164

We report on experiments aimed at precise characterization of the hysteresis loop behavior of permanent magnets by combination of different measuring methods. A discussion is made, in particular, on the application of the Vibrating Sample Magnetometer (VSM), the electromagnet-based hysteresisgraph (EMH), and the Pulsed Field Magnetizer (PFM) methods. In this framework, special emphasis is placed on advantages and shortcomings of the PFM method. Magnetic hysteresis loops have been determined on isotropic and anisotropic Ba ferrites and bonded Nd-Fe-B samples using both spherical (VSM and PFM) and cylindrical (electromagnet and PFM) samples. Overall agreement is found between the results obtained with all different measuring approaches and different sample geometries, but for a definite trend of the measured coercive field value on the impressed field rate. This can be very fast in the PFM testing (period T - 10 ms) and very slow with VSM testing (T - 1800 s), and different magnetic viscosity field contributions are consequently put in evidence. It is shown that PFM can afford both the measurement of the whole sample magnetic moment, exploiting the reciprocity principle, or the conventional fluxmetric measurement in practically sized cylindrical samples. In the latter case, non-homogeneous demagnetizing effects, though accounted for by calculation, can represent a major source of uncertainty when using low aspect ratio test specimens.