Fe films have been prepared by dual ion beam sputtering. The voltage for Ar bombardment V-A was varied in the range between 80 and 2000 V. The relationship between V-A dependence of the properties of the Fe films and the temperature of the film surface has been investigated in detail. The temperature of the substrate holder, Ts increased with an increasing V-A, though the substrate holder was cooled by water. Ts took the maximum value of 120 degrees C at V-A of 2000 V. Taking the Ar bombardment on the film surface into consideration, the kinetic energy of the ion is almost transferred to the thermal energy on the film surface except the energy of the sputtered atoms and recoiled ions. As a result, the pulsed high temperature, that is, the thermal spike effect may appear on the properties of films. So, the temperature elevation T-SPIKE was estimated by a thermal equation. T-SPIKE reached the melting point of Fe near the bombarded position at V-A in the range from 100 to 200 V. V-A indicated good soft magnetic films in agreement with the range. It may be necessary to improve the properties such that the temperature elevation by Ar bombardment is near the melting point of Fe. This model of the thermal spike may estimate the optimum condition of ion bombardment for the different him deposition and apparatus.