Title :
Measuring the coercivity of individual sub-micron ferromagnetic particles by Lorentz microscopy
Author :
Salling, C. ; Schultz, S. ; McFadyen, I. ; Ozaki, M.
Author_Institution :
California Univ., San Diego, CA, USA
fDate :
11/1/1991 12:00:00 AM
Abstract :
The Foucault mode of Lorentz microscopy has been applied to detect the polarity of the magnetic field produced by ferromagnetic particles in the single-domain size range. One can follow the polarity of any given particle through multiple cycles of removal and return of the sample from the transmission electron microscope. Hence, one can determine the particle coercivity by applying a sequence of known fields to the sample. The proposed 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. The authors demonstrate the ability to detect the polarity and measure the coercivity of nearly ellipsoidal γ-Fe2O3 particles which have a moment of ~10-13 emu
Keywords :
coercive force; ferrites; ferromagnetism; iron compounds; magnetic properties of fine particles; magnetic variables measurement; magnetisation reversal; transmission electron microscope examination of materials; transmission electron microscopy; Foucault mode; Lorentz microscopy; ferromagnetic particles; gamma Fe2O3 particles; magnetic field; magnetization reversal mechanism; particle coercivity; polarity; single-domain size range; transmission electron microscope; Assembly; Coercive force; Magnetic field measurement; Magnetic force microscopy; Magnetization reversal; Morphology; Particle measurements; Physics; Testing; Transmission electron microscopy;
Journal_Title :
Magnetics, IEEE Transactions on