Dresden 2017 – scientific programme

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MA: Fachverband Magnetismus

MA 10: Caloric Effects in Ferromagnetic Materials

MA 10.2: Talk

Monday, March 20, 2017, 15:30–15:45, HSZ 04

Simulation of complex magnetic intermetallics for ferroic cooling — •Peter Entel and Markus Gruner — Faculty of Physics, University Duisburg-Essen, 47048 Duisburg, Germany

We discuss the structural and magnetic properties of magnetic Heusler intermetallics like Ni-Mn-(Ga, In, Sn) doped with Co, which undergo a magnetostructural phase transition if rapidly quenched. This leads to a large inverse magnetocaloric effect. The coupling of structural and magnetic degrees of freedom is an intrinsic effect and can be explained by a microscopic itinerant band model where electrons are coupled to tetagonal distortions. The model explains why martensitic instability and high-spin state (ferromagnetic order) are mutually exclusive and only distortion and low-spin state (antiferromagnetic order) may coexist. Under magnetic field we observe kinetic arrest phenomena. For the materials which are less rapidly quenched, this magnetostructural phase transition shows time-dependent effects and starts to fade away and phase segregation into cubic ferromagnetic Heusler phase and tetragonal antiferromagnetic Ni-Mn phase occurs for all Mn excess Heusler alloys in agrement with experimental findings [1].

[1] A. Cahir, M. Acet, M. Farle, Sci. Rep. 6, 29831 (2016)