We study the dependence of the magnetocaloric effect on the magnetic field-change-rate the first order magnetostructural transition in Mn 3 GaC by measuring the adiabatic temperature change DT at three different time scales: 11 mT s À1 , 700 mT s À1 , and $1000 T s À1. We find that the maximum adiabatic temperature-change of about 5 K is reached in the 11 mT s À1 and 700 mT s À1 rates, whereas for the $1000 T s À1-rate the transition lags the change in the magnetic field so that the maximum adiabatic temperature-change is not attained. V
Thermal-hysteresis affects adversely the reversibility of the magnetocaloric effect around a first order magnetostructural transition. In Mn3GaC, a first order antiferromagnetic-ferromagnetic transition is accompanied by a volume-change and a 5 K thermal-hysteresis. We study the reversibility of the magnetocaloric effect in the transition region by direct adiabatic temperature-change measurements. The magnetic field is cycled between 0 and 3 T, and the temperature-change is observed. We find that the system exhibits a temperature-change of 3.1 K in the virgin state, and all subsequent cycling leads to a 2.8 K warming and cooling when the field is decreased and increased, respectively.
Mn2−xCrxSb exhibits an antiferromagnetic-ferrimagnetic transition of which the temperature can be changed by controlling the Cr concentration. Increasing the Cr content from x = 0.05 to 0.13 raises the transition temperature from about 180 K up to around room temperature. To suppress the inevitable ferromagnetic MnSb impurity phase, we partially replace Sb by In. Mn2−xCrxSb1−yIny alloys have an antiferromagnetic-ferrimagnetic transition and a narrow transition hysteresis and exhibit the inverse magnetocaloric effect. We examine the magnetocaloric effect from the magnetization and direct adiabatic temperature-change measurements.
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