The magnetodielectric effect of Fe3O4 nanoparticles and polydimethylsiloxane (PDMS) nanocomposites is reported.The fabrication method of nanocomposites is proposed

and a series of tests on composites including structural characterization

magnetic properties

dielectric properties are performed.It can be concluded that the magnetic properties of the composites depend on the nanoparticle's magnetization.The dielectric constant of the composites with zero magnetic field is increasing with the increase of the nanoparticle concentration

which is consist with the Maxwell-Wagner model.The variation mechanism of relative permittivity as a function of applied magnetic field and the magnetodielectric effect of nanocomposites with different sizes and concentrations of nanoparticles are mainly investigated.The results show that the variation of difference relative permittivity with hysteresis is increasing with the increase in magnetic field.The nanocomposites relative permittivity variation with magnetic field increases as increasing the concentration and the size of nanoparticles.However

the permittivity variation hysteresis of the nanocomposites with bigger nanoparticles is also larger.The studies confirm that the magneticdielectric effect can be observed when the composites are placed in magnetic field

and the variation rate

saturation and hysteresis of the nanocomposites relative permittivity with magnetic field are affected by the concentration and the magnetic properties of nanoparticles including permeability

saturation magnetization and coercivity.