In the presented study Gd and the alloy Fe49Rh51 are considered to be possible magnetocaloric materials for a new hyperthermia method. From general principles of thermodynamics a new mathematical model allowing the calculation of heat transport in a tumor was developed and numerical simulations were performed. The heating-up time as a dependence of the size and mass of a spherical tumor is determined. Estimates of the necessary frequency in dependence of the particle concentration and temperature are presented. In the case of Gd nanoparticles, approximate and accurate calculations are made by assuming that the covering material ofthe particles consist of poly(N-isopropylacrylamide) hydrogel. Dynamic heat transfer processes are graphically visualized.