Magnetic caloricsCopyright: © FZ Jülich
(Multi)Caloric materials, which undergo a reversible thermal change when an external field is applied/withdrawn, are promising candidates in energy-efficient solid-state cooling devices. They can be classified as: magnetocalorics (magnetic field), electrocalorics (electric field), elastocalorics (stress), and barocalorics (pressure). A coupling of several of these effects may increase this applications potential.
Our research mainly focuses on compounds in intermetallic systems (e.g. Mn5-xFexSi3-yGey), which exhibit the magnetocaloric effect (2-4 J/kg K) at low magnetic field (~2 T), and on spin crossover compounds that have the barocaloric effect (40-80 J/kgK) at low hydrostatic pressures (~1 GPa). The large entropy changes in these materials originate from both spin ordering and lattice vibrations that are strongly coupled.
The overall objective of our research is to understand the underlying mechanisms of the caloric effects, the interaction of the lattice with magnetic and electronic degrees of freedom and its evolution with external stimuli such as chemical composition, pressure, temperature or magnetic field. We also optimize these materials to obtain large caloric effects at small driving fields.
We employ neutron and x-ray powder and single crystal diffraction and inelastic neutron scattering under different external stimuli as well as various physical property measurements. Our aim is to exploit the material properties for real life applications in refrigeration based on solid-state caloric effects.
See also information of the project at FZ Jülich.
Prof. Dr. Karen Friese
Dr. Andrzej Grzechnik
N. Maraytta, J. Voigt, C. Salazar Mejía, K. Friese, Y. Skourski, J. Perßon, S. M. Salman, and T. Brückel, Anisotropy of the magnetocaloric effect: Example of Mn5Ge3 , Journal of Applied Physics 128, 103903 (2020)
A. Eich, A. Grzechnik, L. Caron, Y. Cheng, J. Wilden, H. Deng, V. Hutanu, M. Meven, M. Hanfland, K. Glazyrin, P. Hering, M. G. Herrmann, M. Ait Haddouch, and K. Friese, Magnetocaloric Mn5Si3 and MnFe4Si3 at variable pressure and temperature, Materials Research Express 6, 096118 (2019)
N. Maraytta, Y. Skourski, J. Voigt, K. Friese, M. G. Herrmann, J. Persson, J. Wosnitza, S. Salman, and T. Brückel, Direct measurements of the magneto-caloric effect of MnFe4Si3 in pulsed magnetic fields, J. Alloys Comp. 805, 1161 (2019)
J. Wilden, A. Hoser, M. Chikovani, J. Persson, J. Voigt, K. Friese, and A. Grzechnik, Magnetic Transitions in the Co-Modified Mn2Sb System, Inorganics 6, 113 (2018)
S. Gallus, M. Ait Haddouch, M. Chikovani, J. Persson, J. Voigt, K. Friese, A. Senyshyn, and A. Grzechnik, Crystal structure and magnetism of the FexNi8-xSi3 materials, 0 ≤ x ≤ 8, Solid State Sciences 76, 57 (2018)Copyright: © BMBF
This project is funded by the BMBF as part of the program cooperation with developing and emerging countries in the Middle East, North Africa, Turkey (Project MagCal, No. 01DH17013)Copyright: © PGSB
and as part of the Palestinian-German science bridge.