Magnetic properties of acicular γ-Fe
2O
3 particles for magnetic recording media derived from goethite particles are regulated directly by controlling the morphology of goethite particles. The shape and magnetic properties of acicular γ-Fe
2O
3 by oxidizing weakly alkaline solution are examined by varying conditions: the initial Fe
2+ concentration, the neutralization molar ratio in the seed reaction, and the partition of the rate of Fe
2+ consumption either by the seed reaction or by the growth. Possible ranges of control are 200-300nm for the particle sizes, and 8 to 14 for the aspect ratio, while the S. D. of the aspect ratio between 2.5 to 5. Consequently, desirable acicular γ-Fe
2O
3 with a higher SQ and a lower SFD in the hysteresis curve can be synthesized.
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