MAGNETIC-ORDERING IN THE GARNET YCA2SBFE4O12

The magnetic order in YCa2[SbFe](Fe-3)O-12 is very complex and field-d ependent due to the substitution of diamagnetic Sb5+ ions on the octah edral sublattice. The magnetic behavior differs from that observed in Y2Ca[ZrFe](Fe-3)O-12 presumably due to charge differences on the subst ituted cations. The main ferrimagnetic transition due to a-d coupling of the octahedral and tetrahedral sites is very broad and extends down to ca. 140 K. Below this temperature, the antiferromagnetic d-d excha nge on the tetrahedral sites becomes significant and is thought to cau se canting of the tetrahedral moments. At 10 K, the moments at both oc tahedral and tetrahedral sites determined by powder neutron diffractio n-2.2(2) and 1.5(1) mu(B) respectively-are very low and are consistent with significant canting on both cation sublattices. Mossbauer spectr oscopy revealed five nonequivalent tetrahedral sites which relate to t he occupation of nearest neighbor octahedral sites by a statistical di stribution of Sb5+ and Fe3+ ions. (C) 1995 Academic Press, Inc.