Influence of densification on the remanence, the coercivities and the interaction field of elongated γFe2O3powders

The influence of densification on the remanence, the coercivities and the interaction field was measured for two differing powders of γFe
2
O
3
. The coercive force H
c
and two remanence coercivities H
r
and H'
r
(deduced from d.c. demagnetization and static remanence curves, respectively) vary linearly on compression, as does the coercivity factor (H
r
-H
c
)/H
c
and the interaction field factor (H'
r
-H
r
)/H
c
. For zero values of the last factor, the first factor tends to a value close to that predicted, and H
c
values for this noninteracting limit were deduced which agree with incoherent magnetization reversals. The two specimens have differing characteristic slopes of curves of H
c
against (H'
r
-H
r
)/H
c
and at higher comppressions particle breakage is made manifest. The remanence ratio decreases non-linearly on compression. A qualitative discussion of all data involves the partial formation of particle clusters.