Assessment of the magnetocaloric effect in La,Pr(Fe,Si) under cycling

• Measurement protocols are presented to assess materials for magnetic refrigeration.
• Entropy changes are compared to the temperature change under adiabatic conditions.
• The procedure overcomes limitations of the Maxwell relation for first order materials.
• The first order magnetocaloric material La0.6Pr0.4(Fe,Si)13 is investigated.

The response of a magnetocaloric material to periodic variations of magnetic field and temperature corresponding to those occurring during a magnetic refrigeration process is studied. A series of simple measurement protocols are suggested which are used to obtain a value for the cyclic response of the magnetic entropy change associated with the magnetic transition. The entropy values are compared to direct measurements of the temperature change under adiabatic conditions. The procedure is illustrated on the first order magnetocaloric material La0.6Pr0.4Fe11.6Si1.4 and provides a basis for comparison of the suitability of different hysteretic magnetocaloric materials for application in a magnetic refrigerator. For the alloy studied here the peak magnetic entropy change of −28±1 J kg−1 K−1 in a field change of 2 T is not affected by cycling, but the full width at half maximum of the peak decreases from 8.7 K to 3.8 K.