Gyrotropic Susceptibility of Polycrystalline Ferrites Magnetized at Remanent State

Taking into account the internal dipolar effect, the r.f. susceptibility tensor is calculated for polycrystalline ferrite in three magnetization states : at saturation, at remanent state, and unmagnetized. The use of ferrites and garnets is limited in VHF range by "the low field losses". It is well known that these losses result from internal dipolar effects, which appear as soon as the ferrites are not completely saturated |1| |2|. The r.f. domain\´s internal field h¿i results from the macroscopic r.f. field applied into the sample, corrected by the field of r.f. magnetic internal charges. Previously |3| a Lorentz formalism has been proposed for this demagnetizing field h¿i = h¿a + |N| (¿ - m¿) (1) The validity of this rough formalism can be compared to the Weiss molecular field for the exchange energy.