Permeability and ferromagnetic resonance line width of some ferrites with garnet structure

Some substitutions have been carried out in yttrium-iron garnet (Y3Fe5O12) which have a marked influence on its properties. Small amounts of calcium decrease losses in the permeability in the frequency range 104¿106c/s. The same can be accomplished by a small iron deficiency or a very careful method of preparation. Iron excess or substitution of tetravalent ions such as Ti4+ or Si4+ for iron gives rise to high losses in this frequency range. Combined substitutions of a divalent ion and a tetravalent ion such as Ca + Si and Ca + Ti for Y + Fe can be carried out in higher concentrations. The low-temperature magnetic moment decreases with the amount of silicon and increases with the amount of titanium. In the latter case the l.f. permeability increases to over 400. The losses in the kilocycle per second range can be reduced again with a small extra amount of calcium. The ferromagnetic line widths at 3cm of several samples have been measured and are usually found to lie between 50 and 100 Oe. The resistivity of nearly all samples is higher than 107¿-cm.