Structural and magnetic properties of R(Fe[sub 1-y]Co[sub y])[sub 12-x]Nb[sub x] compounds.

The magnetic properties of RFe[sub 12-x]Nb[sub x] and R(Fe[sub 1-y]Co[sub y])[sub 11.3]Nb[sub 0.7] compounds with R=Y, Tb, and Dy have been investigated in the concentration region defined by 0.6<x<0.8 and y≤0.3, where the compounds are single phase with the ThMn[sub 12]-type of structure. The Curie temperature T[sub C] of the RFe[sub 12-x]Nb[sub x] compounds is almost independent of the Nb content whereas the saturation magnetization M[sub s] decreases with increasing Nb content. The spin-reorientation temperature T[sub sr] of the TbFe[sub 12-x]Nb[sub x] and DyFe[sub 12-x]Nb[sub x] compounds decreases monotonically with increasing x. Substitution of Co for Fe in RFe[sub 11.3]Nb[sub 0.7] leads to a remarkable increase of T[sub C] and the appearance of a maximum in the Co-concentration dependence of M[sub s]. In contrast, T[sub sr] decreases monotonically with increasing Co content for both R=Tb and Dy. The modification of T- and R-sublattice anisotropy originating from a change of the Nb content and from substitution of Co for Fe was analyzed by combining crystalline electric field theory and the individual-site model. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]