Makeup and uses of a basic magnet laboratory for characterizing high-temperature permanent magnets

A set of instrumentation for making basic magnetic measurements was assembled in order to characterize high-intrinsic-coercivity, rare-earth permanent magnets with respect to short-term demagnetization resistance and long-term aging at temperatures up to 300{degrees}C. The major specialized components of this set consist of a 13-T-peak-field, capacitor-discharge pulse magnetizer; a 10-in.-pole-size, variable-gap electromagnet; a temperature-controlled oven equipped with iron-cobalt pole piece extensions and a removable paddle that carries the magnetization and field sensing coils; associated electronic integrators; and standards for field intensity H and magnetic moment M calibration. A 1-cm cubic magnet sample, carried by the paddle, fits snugly between the pole piece extensions within the electrically heated aluminum oven, where fields up to 3.2 T can be applied by the electromagnet at temperatures up to 300{degrees}C. A sample set of demagnetization data for the high-energy Sm{sub 2}Co{sub 17} type of magnet is given for temperatures up to 300{degrees}C. These data are reduced to the temperature dependence of the M-H knee field and of the field for a given magnetic induction swing, and they are then interpreted to show the limits of safe magnet operation.