Magnetoplumbite-type hexagonal ferrite and method for producing radio wave absorber

A method for producing a powder of a magnetoplumbite-type hexagonal ferrite which is an aggregate of particles of a compound represented by Formula (1), the method comprising:

• a step A of adjusting a pH of an aqueous solution containing a Fe salt, an Al salt, and at least one metal element salt selected from the group consisting of a Sr salt, a Ba salt, a Ca salt, and a Pb salt to exceed 8.0, thereby obtaining a reaction product;
• a step B of drying the reaction product obtained in the step A, thereby obtaining a dried product;
• and
• a step C of firing the dried product obtained in Step B, thereby obtaining a fired product,
• AFe(12-x)AlxO19 Formula (1)
• in Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0,
• wherein, in the step A, a liquid temperature of the aqueous solution is 15° C. to 40° C.