Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 61: Caloric Effects

MA 61.3: Talk

Friday, March 20, 2020, 10:00–10:15, HSZ 101

Optimizing the magnetocaloric effect in all-d-metal Ni-Co-Mn-Ti Heusler alloys — •Benedikt Beckmann, Andreas Taubel, Lukas Pfeuffer, Franziska Scheibel, Konstantin Skokov, and Oliver Gutfleisch — Institut für Materialwissenschaft, TU Darmstadt, 64287 Darmstadt, Germany

Magnetocaloric refrigeration is a promising cooling technology which could be an environmentally friendly and more energy efficient alternative to conventional vapor compression refrigeration. Among magnetocaloric materials, Ni-Mn based Heusler alloys, showing a first-order magnetostructural phase transition, are promising candidates. In this study, we carried out a systematic analysis of all-d-metal Ni50-xCoxMn50-yTiy Heusler alloys. Due to their enhanced mechanical stability and large volume change, these alloys could be used for cooling cycles that use magnetic field and pressure as external stimuli for inducing the phase transition. A systematic heat treatment optimization is carried out, resulting in a substantial decrease of the transition width down to only 4 K. The microstructural differences between the as-cast and differently annealed alloys are analyzed in detail by in-situ Kerr microscopy. As a result, large isothermal entropy changes of up to 38 Jkg^-1K^-1 in 2 T are achieved. The adiabatic temperature change is measured directly for this material system and values of up to -3.8 K for the first field application and -0.8 K under cyclic conditions are obtained in moderate magnetic field changes of 2 T.

We acknowledge financial support from ERC (Advanced Grant "Cool Innov", No. 743116) and DFG (CRC/TRR 270).