Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 38: Magnetocaloric Effects (joint session MA/TT)
TT 38.2: Vortrag
Dienstag, 13. März 2018, 09:45–10:00, EB 407
Spin dynamics of magnetocaloric compounds under magnetic field investigated with inelastic neutron scattering measurements — •Nikolaos Biniskos1,2, Karin Schmalzl1, Stephane Raymond2, and Thomas Brückel3 — 1Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at ILL, 71 avenue des Martyrs, 38000 Grenoble, France — 2Univ. Grenoble Alpes, CEA, INAC, MEM, 38000 Grenoble, France — 3Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS-2) and Peter Grünberg Institut (PGI-4), JARA-FIT, 52425 Jülich, Germany
The magnetocaloric effect (MCE) is a temperature or entropy change of a material subject to a variation of magnetic field and is the basic principle of magnetic refrigeration. This technique is considered as promising for a more environmentally friendly and efficient use of energy. However, the microscopic mechanisms at play are to be revealed and the key ingredients are to be identified in order to design new materials. In order to understand the fundamental driving force of the MCE, a microscopic study of magnetism with inelastic neutron scattering (INS) measurements is necessary. To this aim, the spin dynamics of MnFe4Si3 and Mn5Si3, that exhibit the direct and inverse MCE, respectively, have been investigated with INS measurements under different magnetic fields and temperatures. It is evidenced that the inverse MCE of Mn5Si3, the cooling by adiabatic magnetization, is associated with field induced spin-fluctuations, contrary to the usual suppression of fluctuations by a magnetic field that is observed in the direct MCE of MnFe4Si3 [1]. [1]N. Biniskos et al., Phys. Rev. B 96 104407 (2017).