Perturbation of magnetization of a magnetic fluid by ultralow thermal fluctuations accompanying a sound wave

The paper presents the results of theoretical and experimental research of the the effect of perturbation of the magnetization of a magnetic fluid caused by thermal fluctuations in an adiabatic sound wave in the initial area of the magnetization curve. Measurements are conducted on samples of a magnetic colloid with various viscosity of the dispersion medium in the frequency range of 20–60 kHz. In this frequency range, the studied samples are characterized by the absence of thermal relaxation of magnetization. Comparison of the conclusions of the thermal magnetization relaxation model with the results of experiment make it possible to obtain information on the rheological features of the neareast molecular environment of a particle, i.e., nanorheology.