Intrinsic coercive force variation with packing in fine particle assemblies

A formula is given to describe the variation of intrinsic coercive force with packing in elongated single domain (ESD) iron particle assemblies. A similar formula, which describes this variation in barium ferrite particle assemblies, is formally identical to the other one by simply changingp(packing) into1 - p(porosity). Magnetic interactions are considered, and an overall interaction field is defined that may account for intrinsic coercive force variations in the case of ESD iron particles. Experimental results on barium ferrite particle assemblies are presented that suggest the existence of a critical packing factor (p ~ 0.15) separating two different, but not specified, modes of interaction.