In the present work, we model the salient magnetic properties of the alloy layered ferrimagnetic nanostructuresbetween magnetically ordered cobalt leads. The effective field theory (EFT) Ising spin method is used to compute reliable J Co−Co and J Gd−Gd exchange values for the pure cobalt and gadolinium materials in comparison with experimental data. Using the combined EFT and mean field theory (MFT) spin methods, the sublattice magnetizations of the Co and Gd sites on the individual hcp basal planes of the layered nanostructures, are calculated and analyzed. The sublattice magnetizations, effective magnetic moments per site, and compensation characteristics on the individual hcp atomic planes of the embedded nanostructures are presented as a function of temperature and the thicknesses of the layered ferrimagnetic nanostructures, for different stable eutectic concentrations c ≤ 0.5. In the absence of first principles calculations for these basic physical variables for the layered nanostructures between cobalt leads, the combined EFT and MFT approach, and appropriate magnetic modeling of the well-defined interfaces of these systems, yield the only available information for them at present. These magnetic variables are necessary for spin dynamic computations, and for the ballistic magnon transport across embedded nanojunctions in magnonics. The model is general, and may applied directly to other composite magnetic elements and embedded nanostructures.