The Properties of Ferromagnetic Compounds at Centimetre Wavelengths

The magnetic and dielectric properties of γ-ferric oxide, magnetite, Mn-Zn ferrite and Ni-Zn ferrite have been measured at wavelengths from 60 cm. to 1.23 cm. The pronounced magnetic dispersion and absorption which occur are attributed to the decay of the rotational magnetization, due to Larmor spin resonance in the internal anisotropy field HN. The theoretical relation HN = 2K/M, where K is the anisotropy coefficient, and M the saturation intensity, agrees satisfactorily with the observations, and|K| has been derived for each material. An inverse relationship between HN and the initial susceptibility is shown to account quantitatively for the magnetic resonance observed in high-permeability materials at much lower frequencies