| 摘要 |
High-energy permanent magnetic materials are characterised by exposing the material to sequential pulsed fields of respectively different rates of change of magnetic field strength, sensing the total magnetic field strength, sensing the total magnetic fields generated in the sample (11) by the respective pulses including eddy currents induced therein, and eliminating eddy current components from the said fields, whereby the nett magnetic fields relate to the magnetic characteristics of the sample (11). Preferably the pulsed field is capacitor-generated via a solenoid (12) and the rate of change of the magnetic field strength is produced by holding the waveform constant and altering the pulse duration, for example by providing taps (19) on the solenoid together with an inductor and a balancing resistor, to enable the ratio of resistance to inductance to be maintained substantially constant across the range of taps utilised. |
