Local arrangement of particles in magnetic fluids due to the measurement alternating field

•Changes in the magnetic susceptibility spectrum of ferrofluids are reported.•The samples were subjected solely to the measuring field.•The frequency range of the measuring field was from 50Hz to 13MHz.•The effect is irrespective of the colloidal stability of samples.•The result is ascribed to the local arrangement of particles in alternating field. Changes in the magnetic susceptibility spectrum of ferrofluids, χ(ω), due to the nanoparticle agglomeration are common when a static magnetic field is superimposed on the measuring field, but here we report on changes which occur in the absence of a static magnetic field, solely in the presence of the measuring field, over the frequency range of 50Hz–13MHz and irrespective of the colloidal stability of samples. The result is explained in terms of local rearrangement of particles within ferrofluids subjected to low frequency alternating magnetic field.