CoFe2/CoFe2O4/MgO were built for expanding applications of magnetic particles.
Rattle-type photocatalysts were obtained in the absence of template and etchant.
The rattle-type particles exhibited the strong absorption to methylene blue.
The highest degradation efficiency reached 93% for CoFe2/TiO2.
CoFe2/TiO2 can be easily separated due to its high magnetization.