To provide a method for manufacturing a hexagonal ferrite powder, in which a magnetic recording medium having superior electromagnetic transducing characteristic, superior still durability and superior running durability with respect to head contamination can be obtained, and to provide a magnetic recording medium, using the ferrite powder.
In the method for manufacturing the hexagonal ferrite powder, a process, in which a hexagonal ferrite powder having 10 to 40 nm average particle size and 135 to 400 kA/m coercive force Hc is treated in a slurry state with an organic phosphorous compound, one end of the bivalent organic group of which has a group derived from phosphoric acid and the other end of which has an amino group or a group having an alcoholic hydroxy group, is included. The ferrite power is used for the magnetic recording medium.