Tuning the Curie temperature and thermal hysteresis of giant magnetocaloric (MnFe)2PX (X = Ge and Si) compounds by the Ru substitution

Effects of the Ru substitution on magnetocaloric properties have been studied for MnFeP 0.8 Ge 0.2 and Mn 1.2 Fe 0.8 P 0.5 Si 0.5 . The parent compounds undergo a first-order magnetic transition near room temperature accompanied by a large thermal hysteresis, , of about 10 K. The substitution of 10–15 at. % of Ru reduces down to 2–3 K. On the other hand, a sharp magnetic transition is preserved by the Ru substitution up to 15% and, as a result, a large magnetic entropy change and a small are achieved. It is found that the refrigerant capacity of the Ru substituted compounds is 1.6–1.8 times as large as that of Gd. These results have proved that the Ru substitution is an effective method to realize Mn-based magnetic refrigerant materials.