[en] The group paramagnetism of the ultrafine ferrimagnetic S-FeOOH particles with the help of the Mossbauer effect is studied. The experimental Mossbauer spectra are compared with the spectra calculated according to the Wickman's model for particles of different size. The Wickman's model is found not to be valid for the relaxation spectra calculations when the angle between the effective magnetic field and the axis of electric field gradient on the iron nucleus is other than zero. The Mossbauer spectra form dependence on the distance between particles (magnetic interaction between particles) is studied. The particles are shown to be grouped owing to the magnetic interaction; inside such ''groups'' the magnetic moments of the component particles are correlated. The interparticle magnetic interaction energy is compared with the thermal one