High efficiency direct magnetocaloric effect in Heusler NiMnGa microwire at low magnetic fields

A perspective magnetocaloric Heusler alloy Ni2MnGa in the unique form of a microwire is studied in this work. Magnetic and calorimetric analyses are compared, providing insight into the operating conditions of magnetic refrigeration, which is the essential interconnection of material sciences and device engineering. Presented results describe the highly efficient magnetocaloric effect of Ni2MnGa at low magnetic fields up to 0.3 T. A direct thermometry method, by micro-thermocouple, is employed to directly measure the temperature change of the single piece of a microwire; weighing only 2.36 mg. The mentioned method allows studying the magnetocaloric effect even on the micro-samples in operating conditions. It later allows finding the best conditions, e.g. the temperature range and the amplitude and frequency of the magnetic field change for studied materials.