In the last few years, magnetic nanoparticles have turned out to offer great potential in biomedical applications. This study was focused on MnxFe1-xFe2O4 ferrite particles series with x ranging between 0 and I. Manganese ferrites nanoparticles were prepared by co-precipitation method that allows a good control of their shape and size. The X-ray analysis indicated a crystallite size of the particles in the nanometers domain increasing with the Mn cation substitution level. Average grain size of the nanoparticles calculated from transmission electron microscopy images of the samples was ranging between 10.5 and 19.0 nm suggesting that the majority of the nanoparticles are monodomain. The hydrodynamic diameter of the water dispersed nanoparticles measured by dynamic light scattering was ranging between 60 and 105 nm proving the tendency of agglomeration. Vibrating sample magnetometer measurement confirmed the superparamagnetic behavior of the powders. The magnetic properties were analyzed considering the proposed cation distribution and Yafet-Kittel angles, while the specific absorption rate (SAR) measurement at 1.95 MHz frequency confirmed the influence of substitution level on magnetic properties and thermal transfer rate. From our results the highest value for specific absorption rate was 148.4 W g(-1) for Mn2Fe2O4 at an AC field of 4500 A m(-1). (C) 2013 Elsevier B.V. All rights reserved.