An Approach To A Rationale In Ferrite Synthesis: Evaluation Of Magnetic Moments

Abstract

A systematic development of broad classes of composite ferrites is given in terms of MO or R[subscript 2]O[subscript 3] addition to a mother spinel under three groupings I-I , N-N, I-N which refer to systems involving two inverse spinels, two normal and one of each. The behavior of the related magnetic moments is examined in terms of composition for certain idealized conditions in the light of antiferromagnetic coupling of spins at the tetrahedral and octahedral sites. The conditions under which the magnetic moment shifts in direction (referred to as a reversal effect already observed in the system NiO*(Fe[subscript 2]O[subscript 3])[subscript l-x]*(Al[subscript 2]O[subscript S])[subscript X]) are established so that predictions can be made as to its general occurrence. Certain departures between theoretical and experimental magnetic moment dependence on composition are pointed out, and in particular , the interesting case of MgO*(Fe[subscript 2]O[subscript 3])[subscript l-x]*Al[subscript 2]O[subscript 3] is re-examined by allowance for incomplete inversion in Fe[subscript 2]O[subscript 3] itself—a procedure which still fails to reconcile theory with the reported observation, thus suggesting a closer scrutiny of this system.