Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 53: Joint Session Magnetic Shape Memory Alloys II (jointly with DS, MA)

MM 53.6: Talk

Thursday, March 29, 2012, 16:15–16:30, H 0112

Hysteretic aspects of the inverse magnetocaloric effect in martensitic alloys. — Mehmet Acet¹, •Ivan Titov¹, Antoni Planes², Lluis Mañosa², David Gonźalez-Alonso², and Thorsten Krenke³ — ¹Fachbereich Physik, Experimentalphysik, Universität Duisburg-Essen, D-47048 Duisburg, Germany — ²Facultat de Fisica, Departament d’Estructura i Constituents de la Matéria, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Catalonia, Spain — ³Thyssen Krupp Electrical Steel GmbH, D-4588 1 Gelsenkirchen, Germany

The presence of a large positive entropy change around the martensitic transformation in Ni₅₀Mn₃₅Sn₁₅ and in Ni₅₀Mn_33.5In_16.5 is expected to lead to substantial cooling on applying a magnetic field. However, unlike in Ni-Mn-In, the relatively low temperature-shift of the hysteresis with applied field in Ni-Mn-Sn could limit cooling. In both cases we measure direct temperature-change on applying a magnetic field around the reverse and forward branches of the martensitic transition. In Ni-Mn-Sn we initially detect cooling on applying a magnetic field (inverse MCE) and again further cooling on removing the field (conventional MCE). When the field is reapplied once more we detect only warming due to the irreversibility of the metallurgical state of the alloy. In Ni-Mn-In, the temperature change is largely reversible due to the strong shift in the martensitic transformation temperature with applied field. In this case the metallurgical state of the sample can be partially recovered. The results are discussed in relation to the form of the hysteresis and its thermal shift with applied magnetic field.