A pulsed field magnetometer for analysing the properties of magnetic pigment dispersions used in particulate recording media

摘要

We have designed and developed a pulsed field magnetometer to measure the dynamic properties of magnetic dispersions commonly used in recording media. The instrument produces well defined single-shot field pulses of variable amplitude from 10 Oe to 1270 Oe, adjustable in steps of 10 Oe. Pulse widths of between 4 μs and 127/μs can be selected with a resolution of 1 /μs. The rise and fall times of the pulses are between 1 /μs and 1.5/μs and are symmetrical throughout the range of field amplitudes and pulse widths. Results obtained from the instrument indjcate that it is possible to distinguish between inherent particle switching and physical particle rotation, which is not possible when using conventional AC and DC magnetometers. It has also been found that the instrument may be used in on-line measurements to access the quality of magnetic pigment dispersions used for magnetic tape manufacture.