In the present study, the temperature-dependence of magnetic field effect on the resistance of films of oxides of rare earth elements (Gd, Eu, and Eu-Sin solid solution) prepared by vacuum thermal evaporation was considered and analyzed at approximately the Curie temperature. It was demonstrated that the temperature range of the effect, its sign and magnitude are determined by the dependence of the magnetic moment of magnetic clusters on both the external magnetic field strength and film parameters such as the spin of the magnetic ion, exchange energy, defect density, etc.