The addition of rare ions alters the structure of the powders and decreases the crystalline size, lattice constant, and grain size. The magnetic properties such as saturation magnetization increased due to addition of rare-earth ions in CdFe2O4, Ni-Cu-Zn ferrite.  Magnetic properties depend on the particular method of preparation and additives.Give an example of a decrease in magnetic saturation when rare-earth elements are added to the ferrites.