Regensburg 2022 – scientific programme
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MA: Fachverband Magnetismus
MA 29: Caloric Effects in Magnetic Materials
MA 29.8: Talk
Thursday, September 8, 2022, 11:15–11:30, H47
Magnetocaloric effect of Gd - an realistic ab-initio study — •Rafael Vieira1,2, Olle Eriksson1,3, Torbjörn Björkman2, and Heike C. Herper1 — 1Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden — 2Physics, Faculty of Science and Engineering, Åbo Akademi University, FI-20500 Turku, Finland — 3School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
We present a computational approach to evaluate field-dependent entropy of magnetocaloric materials from ab-initio calculations. Taking hcp Gd as a test system, we fully characterize the entropy associated with the magnetocaloric effect by including the entropy’s electronic, lattice, and magnetic contributions.
The 2nd order nature of the ferromagnetic (FM)→paramagnetic (PM) transition in Gd implies considering intermediate states of magnetic disorder. We describe the properties of these intermediate states as weighted averages of the properties of the FM and PM phases, with mixing weights defined by the magnetization of the system at a given temperature, to which we use the results from the Monte Carlo simulations. This approach allows a realistic system description, bringing the total entropy variation in agreement with reported measurements.
We find, as expected that the magnetic entropy is the dominant entropy. However, we also observe that the lattice contribution has a role in total entropy variation.