Dispersion and absorption in magnetic ferrites at frequencies above one Mc/s

The phenomena of absorption and dispersion observed in magnetic ferrites at frequencies above one Mc/s are discussed making the assumption that at these frequencies no contribution to the magnetisation is made by the Bloch boundaries. For pure and unstrained polycrystalline aggregates of cubic crystals the following relation between the critical frequency ω0 and the initial susceptibility χ is found: ω0·χ=32ƒgƒM, where g = emc = 1.76.106 and M the magnetic moment per cm3. In deriving this equation the damping is assumed to be small. It is further shown that internal stresses tend to increase the losses at lower frequencies and make the rise in tan δ with frequency less steep. This is actually borne out by experiment.