Method of producing hexagonal ferrite and magnetic recording medium using said hexagonal ferrite

摘要

A method of producing hexagonal (system) ferrite, wherein the hexagonal (system) ferrite having an average tabular diameter of 10 to 40 nm and a coercive force (Hc) of 135 to 400 kA/m is treated with an organic compound containing a polar group having an acid dissociation constant (pKa) of 4 or below and/or a salt thereof when the ferrite is recovered and washed, and a magnetic recording medium comprising a support having thereon a non-magnetic layer comprising a non-magnetic powder and on the non-magnetic layer a magnetic layer comprising a ferromagnetic powder, wherein the ferromagnetic powder comprises a hexagonal (system) ferrite magnetic powder having an average tabular diameter of 10 to 40 nm and a coercive force (Hc) of 135 to 400 kA/m and being subjected to treatment with an organic compound containing a polar group having an acid dissociation constant (pKa) of 4 or below and/or a salt thereof.