Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 23: Magnetic Materials and Caloric Effects

MA 23.5: Vortrag

Dienstag, 8. März 2016, 15:00–15:15, H32

Designing cubic Heusler for magnetocaloric-based applications — •Luana Caron¹, Sanjay Singh¹, Sunil W. D’Souza¹, Tina Fichtner¹, Giacomo Porcari², Simone Fabbrici³, Chandra Shekhar¹, Stanislav Chadov¹, Massimo Solzi², and Claudia Felser¹ — ¹Max Planck Institute for Chemical Physics of Solids, Germany — ²Parma University, Italy — ³IMEM-CNR, Italy

Since the observation of a giant magnetocaloric effect (MCE) in Gd₅Ge₂Si₂, the search for materials for MCE-based applications has been focused on compounds showing 1^st order phase transitions. However, the practical application of giant MCE materials is hindered by the nature of the transition itself. In order to drive a 1^st order phase transition, energy is spent to overcome the energy barrier between different states. This energy loss leads to irreversibilities in both temperature and entropy changes in addition to discontinuous structural changes which cause physical instability. In this work we explore theoretically and experimentally how to obtain high magnetic moments in cubic Ni₂(Mn,X)₂ X= Ga, In, Sn Heusler alloys. Our aim is to design Heusler compounds presenting a combination of high ground state moment and a fully reversible 2^nd order phase transition for magnetocaloric cooling applications. Using ab initio calculations we have determined the exchange interactions and magnetic moments of these alloys in the cubic structure as to maximize the net saturation magnetization. As a proof of concept we present the magnetic and MCE properties of the Ni₂Mn_1.4In_0.6 compound which presents a calculated and measured saturation moment comparable to that of Gd.