Angular Variation of the Magnetic Properties of Elongated Single-Domain Iron Particles

Abstract

The demagnetization curves of oriented elongated single-domain (ESD) iron particles have been measured as a function of angle and packing fraction. The reduced coercive forces of dilute compacts show a maximum at an angle of about 50° associated with a buckling magnetization reversal. As the packing fraction is increased,particle magnetostatic interaction lowers the coercive force and suppresses the 50° max. The residual to saturation ratio appears as a distorted cosine function, which the simple single-domain particle model cannot account for without assuming particle orientations inconsistent with electron micrographs. A more realistic model is proposed which accounts for the experimental results by considering the effect on particle domain structure of dendritic branches and cross-links to adjacent particles. The new model has been analyzed by measuring the magnetic properties of arrays of pivoted magnets, which simulate the proposed domain configurations at various angles and packing fractions.