A PULSED-FIELD MAGNETOMETER FOR ANALYZING THE PROPERTIES OF MAGNETIC PIGMENT DISPERSIONS USED IN PARTICULATE RECORDING MEDIA

We have designed and developed a pulsed field magnetometer to measure the dynamic properties of magnetic dispersions commonly used in record ing media. The instrument produces well defined single-shot field puls es of variable amplitude from 10 Oe to 1270 Oe, adjustable in steps of 10 Oe. Pulse widths of between 4 mu s and 127 mu s can be selected wi th a resolution of 1 mu s. The rise and fall times of the pulses are b etween 1 mu s and 1.5 mu s and are symmetrical throughout the range of field amplitudes and pulse widths. Results obtained from the instrume nt indicate that it is possible to distinguish between inherent partic le switching and physical particle rotation, which is not possible whe n using conventional AC and DC magnetometers. It has also been found t hat the instrument may be used in on-line measurements to access the q uality of magnetic pigment dispersions used for magnetic tape manufact ure.