Dresden 2014 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 9: Functional Materials II - Oxides and Alloys

MM 9.2: Vortrag

Montag, 31. März 2014, 12:00–12:15, IFW A

Interface-related phenomena in coupled direct and inverse magneto-caloric materials: A first-principles study — •Biswanath Dutta, Tilmann Hickel, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany

A combination of different magneto-caloric materials in a single system gives rise to new phenomena that can be highly relevant for applications. Within this study, we investigate the physical properties of systems containing Ni-Mn-Ga and Ni-Mn-Sn, which show direct and inverse magneto-caloric effect respectively. X-ray diffraction experiments indicate that their combination in a layered structure significantly changes the structural properties of both phases. We have investigated the underlying mechanisms for this observation using density functional theory. On the one hand, our calculations reveal that the atomic magnetic moments get modified near the interface implying that interfaces influence transition temperatures and entropy changes. On the other hand, we have carefully investigated strain contributions, interlayer diffusion as well as defect formation such as vacancies. Our calculated results show clear indications for Ga diffusion into Ni-Mn-Sn, thereby modifying the chemistry of the alloy. We discuss these results in the framework of lattice expansion and vacancy formation for various species and have used them to explain the experimental observations.