Magnetization curling in perpendicular iron particle arrays (alumite media)

Abstract

Alumite has been investigated by measuring the hysteresis loops for different field directions to determine the influence of the particle interactions in a perpendicular oriented particle medium on the angular dependence of the coercivity and the hysteresis loss. Alumite is an ideal model material for this purpose because the particle size and particle distance are well defined and can be varied independently. It is shown that the coercivity of the particle array can be identified with the nucleation field of one single particle for perpendicular fields. It is clear from the radius dependence of the coercivity that the reversal mode is the curling mode. The angular dependence of the coercivity does not agree with the well-known theoretical curve for one particle, which is caused by the particle interactions. The same can be said about the angular dependence of the hysteresis loss. Calculations of hysteresis loops of particle arrays with interacting particles show the influence of these interactions on the angular dependence of the coercivity.