Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 34: Topical session: Caloric effects in ferroic materials IV - Heuslers

MM 34.2: Vortrag

Mittwoch, 9. März 2016, 12:15–12:30, H39

Impact of point defects on the phase stability in Heusler alloys: A first-principles study — •Biswanath Dutta, Vijaya Begum, Tilmann Hickel, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany

Functional properties of magnetic Heusler alloys such as magnetic shape memory and magnetocaloric effect depend critically on their thermoelastic martensitic transformation. To this end, vacancies can play a decisive role as they control the ordering kinetics in these materials, which has recently been confirmed in experiments. Within this study, we employ density functional theory along with Monte Carlo (MC) simulations to understand the impact of vacancies on the phase stability and transformation behavior in Ni-Mn-based Heusler alloys. Our calculations reveal high vacancy concentrations for Ni and Mn with the vacancy formation energy for Ni being the lowest. We discuss the results in terms of chemical potentials obtained against the formation of different unary and binary phases. The nudged elastic band method is employed to compute the vacancy migration barrier. Our calculated results for the self-diffusion activation energy of vacancies show good agreement with experimental values. Using these results as input for MC simulations we discuss the impact of vacancies on the ordering tendency in these materials.