Hexagonal ferrite powder has an average particle size falling within a range of 10 nm to 50 nm, a switching field distribution SFD23° C. measured at a temperature of 23° C. that is less than or equal to 0.80, and a ratio of a switching field distribution SFD−190° C. that is measured at a temperature of −190° C. to the SFD23° C. (SFD−190° C./SFD23° C.) that is greater than 0.80.