Аннотация:We present results on the investigation of a Fe3O4 ferrofluid based on heavy water, using magnetic measurements. Magnetization curves were generated with an original setup at the Department of Magnetism, Moscow State University. As temperature decreases, the value of the saturation magnetization of the ferrofluid increases. The analysis is carried out using the magnetization curves at the temperatures of 80K and 300K. For the two values of the temperature, we reconstruct the lognormal distribution function of particles diameters. We found a higher value of the mean magnetic diameter and a significantly reduced spread in the values of the diameters at the lower temperature.