Only Ku-band microwave absorption by Fe3O4/ferrocenyl-CuPc hybrid nanospheres

► A novel kind of ferrocenyl-CuPc/Fe3O4 hybrid nanospheres was prepared. ► The hybrids performed microwave absorptivity only in Ku-band. ► The minimum absorbtion of hybrid nanospheres achieved −25 dB. ► The material is believed to have broad application in notch filter in Ku-band.