Particularités de l'effet magnétocalorique dans des phases de Laves de R(Co-Fe)2 à base de terre rare avec R = Ho et Er.

In this paper measurement results of heat capacity (CP) and magnetocaloric effect (MCE) in Ho(Co1-?Fe?)2 and Er(Co1-?Fe?)2 systems over the whole range of Co substitution by Fe are presented. Phase composition was controlled by X-ray diffraction analysis. Heat capacity was measured in the temperature range 77-320 K. MCE has been studied within the temperature range 5-670 K in magnetic fields up to 70 kOe. It was found that Fe concentration increase causes the following: the CP maxima disappearing at urie temperature point and emergence of magnetic contribution to CP in a wide temperature range lower this point; a table-like (plateau) MCE temperature dependence for both magnetic entropy change date (?S) and direct ?T-effect measurements independent on Fe concentration. The possible reasons of such behavior are discussed.