Cobalt ferrite and garnet powders were grown using a conventional ceramic method in two different ways for understanding the magnetic interaction between structurally different materials. Structures of these powders were investigated by using an X-ray diffractometer (XRD) and the magnetic interaction between iron ions and the magnetic properties of the powders were measured by a Mössbauer spectroscopy and a vibrating sample magnetometer (VSM), respectively. The result of the XRD measurement showed that the annealing temperature higher than 1200℃ was necessary to grow a (CoFe₂O₄)_0.5(Y₃Fe₅O₁₂)_0.5 powder. Mössbauer spectra for the powders grown separately and mixed mechanically consisted of sub-spectra of cobalt ferrite and garnet, however, powders annealed together had an extra sub-spectrum, which was related with the magnetic interaction between the grain surface of cobalt ferrite and the one of the garnet. In case of annealing the powders at the temperature large enough to crystallize them, raw chemicals became fine cobalt ferrite and garnet particles at first and then these fine particles were aggregated and formed large grains of ferrite powders. The result of the VSM measurement showed that the powders prepared at 1200℃ had the similar saturation magnetization and the coercivity regardless of the preparation method.