Pulse magnetization measurements in ferrofluids

A pulsed-field (1 μ sec to 3 m sec) inductive magnetometer has been constructed that measures the magnetic moment of a ferrofluid as a function of time. After the applied field is removed, the magnetization is characterized by a fast decay (< 1 μ sec) and a gradual decay that can be as long as 4 msec. The fast component of magnetization varies from about 50% to nearly 100% of the total and we conclude it is due to magnetization processes within the particle. The slow component of magnetization is believed to be due to particle rotation and can be related to particle size through a model developed by Janak.