Adiabatic measurement of the giant magnetocaloric effect in MnAs.

We have studied the compound MnAs with a giant magnetocaloric effect, which has a magneto-structural transition at 316 K. The magnetic phase diagram has been deduced from adiabatic heat-capacity measurements and from cooling and heating curves. The ferroto paramagnetic transition changes with field from 316 K at 0 T to 335.3 K at 6 T. There is a strong thermal hysteresis between 10 and 5 K, depending on field. Direct measurements of the adiabatic temperature change caused by the application of magnetic field were IN made and compared with the values deduced from heat-capacity data. Moreover, adiabatic field cycles were performed quasi-statically between 0 and 6 T around the phase coexistence region, showing the strength of the effect in each phase and on the coexistence lines.