Influence of minor Pr substitution on the magnetocaloric effect of Mn_1−x Pr _x As

The influence of minor Pr substitution on the magnetocaloric effect (MCE) of Mn_1−x Pr _x As (x = 0.005, 0.01, 0.015, 0.02) alloys has been investigated. The lattice parameters a, c and unit cell volume V of the alloys Mn_1−x Pr _x As (x = 0.005, 0.01, 0.015, 0.02) increase monotonically with increasing Pr content. The Pr addition has minor effect on tuning the Curie temperature T _c from 318 K to 321 K for x = 0.005–0.02 and reducing the thermal hysteresis (about 20 K). With increasing the temperature, the critical field induced paramagnetic (PM)–ferromagnetic (FM) transition shifts to higher values. The Pr substitution makes the paramagnetic phase unstable and stabilizes the ferromagnetic phase, which lead to increasing in Curie temperature T _c of Mn_1−x Pr _x As (x = 0.005, 0.01, 0.015, 0.02) alloys. The absence of the huge magnetic entropy change \(\Delta {S}\) spike which was calculated by the Maxwell relation is observed in the temperature range where the stepwise magnetic behaviors occur. The Clausius–Clapeyron equation is used to recalculate the \(\Delta {S}\) of alloys Mn_1−x Pr _x As (x = 0.005, 0.01, 0.015, 0.02) under the conditions of the coexistence of the PM and FM phases. The maximum magnetic entropy change \(\Delta S_{M}^{\max }\) of alloys Mn_1−x Pr _x As (x = 0.005, 0.01, 0.015, 0.02) for a 5 T field change decreases gradually from 30.2 J/kg K to 23.3 J/kg K as Pr increases from 0.005 to 0.02.