Regensburg 2019 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Magnetism Poster A

MA 15.18: Poster

Dienstag, 2. April 2019, 10:00–13:00, Poster E

Effects of decomposition on the magnetocaloric effect in Ni-Co-Mn-In Heusler-based compounds — •Merivan Sasmaz¹, Felix Dreist², Michael Farle², and Mehmet Acet² — ¹Physics Department, Adiyaman University, Adiyaman, Turkey — ²Experimentalphysik AG Farle Universität Duisburg-Essen, Duisburg

Off-stoichiometric Ni-based Heusler compounds in the form Ni₅₀Mn_25+xZ_25−x decompose into full Heusler, Ni₅₀Mn₂₅Z₂₅, and Ni₅₀Mn₅₀ components when annealed in the temperature range 650≤ T≤ 750 K. Compounds that are considered in relation to magnetocaloric effects also fall in this composition range, so that any decomposition resulting from heat treatments can influence the magnetocaloric properties. Here we study systematically the effect of decomposition on the magnetocaloric properties of Ni₄₆Co₇Mn₃₅Z₁₂, which is known to be a prototype inverse magnetocaloric material. We follow the decomposition process from time-dependent magnetization measurements at 750 K and determine entropy-changes from field-dependent magnetization measurements. Although a broadening of the hysteresis increases in the decomposed state, the entropy-change is found to increase, while the martensitic transition temperatures and the Curie temperature shifts, indicating both a change in the composition and the degree of L2₁ ordering.