Regensburg 2016 – scientific programme

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MA: Fachverband Magnetismus

MA 23: Magnetic Materials and Caloric Effects

MA 23.6: Talk

Tuesday, March 8, 2016, 15:15–15:30, H32

Direct measurements of the adiabatic temperature change in shape memory alloys — •Lars Helmich¹, Niclas Teichert¹, Bruno Weise², Anja Waske², and Andreas Hütten¹ — ¹CSMD, Department of Physics, Bielefeld University, Bielefeld, Germany — ²Institute for Complex Materials, IFW Dresden, Dresden, Germany

Magnetocaloric materials are highly promising candidates for efficient cooling devices. Thin film samples represent an ideal system in order to study their suitability for applications. Due to the small sample volume the measurement of the adiabatic temperature change is a challenging task.

Therefore we have set up a new custom-built device which detects Delta T by infrared thermography: The samples are mounted on a nitrogen cooled stage in vacuum giving access to a temperature range between 120K and 470K.

A versatile model for calibration of the infrared emissivity has been developed.

Literature values for bulk Gadolinium are well reproduced with our device. Furthermore the adiabatic temperature change was successfully measured on small-volume Gadolinium melt-spun ribbons. Besides, we have measured ΔT on various Ni-Mn-based Heusler alloys.

In particular we have investigated the Martensitic transformation and magnetic properties in off-stoichiometric NiCoMnAl melt-spun ribbons.