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 γFe2O3. The coercive force Hcand two remanence coercivities Hrand H´r(deduced from d.c. demagnetization and static remanence curves, respectively) vary linearly on compression, as does the coercivity factor (Hr-Hc)/Hcand the interaction field factor (H´r-Hr)/Hc. For zero values of the last factor, the first factor tends to a value close to that predicted, and Hcvalues for this noninteracting limit were deduced which agree with incoherent magnetization reversals. The two specimens have differing characteristic slopes of curves of Hcagainst (H´r-Hr)/Hcand 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.