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TT: Fachverband Tiefe Temperaturen

TT 38: Magnetocaloric Effects (joint session MA/TT)

TT 38.7: Vortrag

Dienstag, 13. März 2018, 11:00–11:15, EB 407

Influence of substitutions, hydrostatic pressure and magnetic field on the MnNiGe system — •Andreas Taubel, Tino Gottschall, Maximilian Fries, Tom Faske, Konstantin P. Skokov, and Oliver Gutfleisch — TU Darmstadt, Institute of Material Science, Alarich-Weiss-Str. 16, 64287 Darmstadt, Germany

An enhancement in the energy efficiency of cooling devices for household refrigeration and air conditioning can provide worldwide savings in energy and CO₂ emissions. An alternative to conventional gas compression refrigerators is solid state based magnetocaloric cooling with the potential of increased energy efficiency. The MM’X materials family provides promising magnetocaloric effects with sharp phase transitions for the MnNiGe and MnCoGe systems.

We studied the isostructural substitutions of Fe for Mn and Si for Ge, which enhance the ferromagnetic character of the low temperature phase, allow for a precise tuning of the transition temperature and reduce the amount of expensive Ge in the compounds. Since a magnetic field shifts the transition temperature by 1 K T⁻¹, the phase transition cannot be induced completely in small fields. We directly measured a maximum adiabatic temperature change of 1.3 K for the first magnetic field application of 1.93 T [1]. Therefore, the large sensitivity towards hydrostatic pressure (72 K GPa⁻¹) enables an additional stimulus to induce the phase transition more efficiently for Fe- and Si-substituted (Mn,Fe)Ni(Ge,Si) compounds.

This work was supported by DFG (Grant No. SPP1599).

[1] A. Taubel et al., J. Phys. D: Appl. Phys. 50, 464005 (2017)