Modulating the phase transition temperature of giant magnetocaloric thin films by ion irradiation

Magnetic refrigeration based on the magnetocaloric effect at room temperature is one of the most attractive alternatives to the current gas compression/expansion method routinely employed. Nevertheless, in giant magnetocaloric materials, optimal refrigeration is restricted to the narrow temperature window of the phase transition (T_c). In this work, we present the possibility of varying this transition temperature in the same giant magnetocaloric material by ion irradiation. We demonstrate that the transition temperature of iron rhodium thin films can be tuned by the bombardment of ions of Ne^{5 +} with varying fluences up to 10¹⁴ ions cm^-2, leading to optimal refrigeration over a large 270-380 K temperature window. The T_c modification is found to be due to the ion-induced disorder and to the density of new pointlike defects. The variation of the phase transition temperature with the number of incident ions opens new perspectives in the conception of devices using giant magnetocaloric materials.