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we have demonstrated that the high frequency properties of superparamgnetic Fe3O4 NPs can be tuned via dipolar interaction.The cut-off frequency can exceed the natural resonance frequency by superparamagnetic/ferromagnetism transition.The finding of non-resonant mechanism in superparagnetic NPs provides us a new approach to tune high frequency over several GHz beyond the Snoek limit.Futhermore,we report a simple procedure for fabricating flexible,free-standing,and magnetic film of GO/CNT–Fe3O4 composites by using a one-pot co-precipitation in situ growth route.Characterizations including X-ray diffraction,Raman spectroscopy,superconducting quantum interference device magnetometry,scanning electron microscopy and transmission electron microscopy have been carried out to investigate the morphology,crystalline structure and magnetic properties of the composites.The layered structure of the as-prepared composites is porous and superparamagnetic.The GO/CNT–Fe3O4 composites exhibit excellent microwave absorbing properties in the range of 2–18 GHz and are expected to be promising candidates as microwave absorbing materials.