About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
IEEE Transactions on Magnetics
Paper
Measuring the coercivity of individual sub-micron ferromagnetic particles by Lorentz microscopy
Abstract
We have applied the Foucault mode of Lorentz microscopy to detect the polarity of the magnetic field produced by ferromagnetic particles in the single-domain size range. We can follow the polarity of any given particle through multiple cycles of removal and return of the sample from the Transmission Electron Microscope(TEM). Hence, we can determine the particle's coercivity by applying a sequence of known fields to the sample. Our technique makes it possible to obtain unambiguous data for the dependence of an individual particle's coercivity on the orientation of the applied field, and the particle's dimensions. Both these data are needed to determine the magnetization reversal mechanism in single-domain particles. In the present paper we demonstrate the ability to detect the polarity, and measure the coercivity, of nearly-ellipsoidal ϒ-Fe<inf>2</inf>O<inf>3</inf> particles which have a moment of ~10<sup>-13</sup>emu. © 1991 IEEE