Local arrangement of particles in magnetic fluids due to the measurement 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 50 Hz-13 MHz 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.