For fine, acicular skeleton particles of
-Fe prepared from
-FeOOH, the effect of interparticle interaction on the angular variation of
H
c was numerically investigated using a direct expansion scheme of the
chain-of-spheres
fanning model to an interacting chain system forming an orthorhombic type of regular space lattice. The model theory reveals that only magnetostatic lateral interchain interaction can affect the angular variation of
H
c. The results have been used to explain the experimentally observed effects of particle morphology and packing fraction on the angular variation of
H
c in systems made from fine acicular particles prepared for audio/video magnetic recording media. It is suggested that a local aggregate of the so-called
multiple
type, is unavoidably generated in the system.