Magnetoplumbite-type hexagonal ferrite powder, radio wave absorber, and method of controlling resonance frequency of magnetoplumbite-type hexagonal ferrite powder

A method of controlling a resonance frequency of a magnetoplumbite-type hexagonal ferrite powder, the method comprising:

• adjusting a magnetic field strength Ha which corresponds to 90% of a magnetization quantity obtained in a case where an external magnetic field of 50 kOe is applied to a magnetoplumbite-type hexagonal ferrite powder within a range satisfying 19 kOe≤Hα≤28 kOe, the magnetoplumbite-type hexagonal ferrite powder comprising a powder of a compound represented by Formula (1):
• AFe(12-x)AlxO19 Formula (1)
• wherein 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 the magnetoplumbite-type hexagonal ferrite powder comprises a compound represented by Formula (2):
• AaAl2O4 Formula (2)
• wherein in Formula (2), Aa represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and
• wherein a ratio x′ of aluminum atoms with respect to 100 atom % of iron atoms in the magnetoplumbite-type hexagonal ferrite powder is from 1.80 to 2.65.