The measurement of the anisotropy field of single "tape" particles

The uniaxial anisotropy field Haof nominally single acicular particles was measured by three different methods, and the coercivity was also found. A very dilute suspension was made in a viscous liquid, and a particle observed with the microscope. Various types of magnetic field were then applied, and the particle\´s change in orientation enabled and/or Hrto be determined. One method gave anomalously low values for Ha, but it was possible to reconcile the results. The larger values lay in a range consistent with the chain-of-spheres and prolate ellipsoid models. There was a linear relationship between Haand Hr(or Hc). The results suggested new reversal mechanisms.