The predictions of a newly developed Bloch-Bloembergen alike analytic magnetization model are compared to experimental results. The effect of size polydipersity on the specific absorption loss is demonstrated for the magnetic nanoparticles containing media. Specific absorption rate shows resonance like behivior as a function of particle size. The obtained results are in excellent agreement with experimental data. The dominace of the Neel relaxation over the Brownian one is demonstrated.