MEASURING THE MAGNETIC-PROPERTIES OF A MICROSCOPIC PARTICLE

A method has been devised for measuring the magnetic properties of single particles of magnetic tape. Since such particles are extremely small (about 0. 5 to 1 mu m long) an exceptionally sensitive method of measurement is needed. The new method is based on a determination of the rate at which a particle in suspension in a viscous fluid, after magnetization by a pulsed field of known value, rotates in the fluid when subjected to a weak opposing external field. A curve giving the relationship between magnetizing field and remanent magnetization is shown for a gamma -Fe//2O//3 particle and a similar one for a CrO//2 particle.