Dresden 2014 – scientific programme

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MA: Fachverband Magnetismus

MA 19: Poster I

MA 19.24: Poster

Tuesday, April 1, 2014, 13:00–15:30, P1

Direct Measurement of the Magnetocaloric Effect via Magneto-modulation Infrared Radiometry — •Jago Döntgen, Jörg Rudolph, and Daniel Hägele — AG Spektroskopie d. kondensierten Materie

The temperature change ΔT exhibited by a material under adiabatic application of a magnetic field is of major interest for both the understanding of its magnetocaloric properties and the assessment of its potential as an energy efficient magnetic refrigerant. The systematic investigation of materials with varying element compositions requires a method to measure temperature changes in small volume samples or even thin films which excludes traditional calorimetry. Here, we measure the temperature change of low volume samples via detection of its thermal radiation in a magnetic field that is modulated at frequencies of up to 100 Hz with up to 40 mT amplitude. The fast modulation establishes adiabatic conditions by keeping up with the fast thermal equilibration of small samples. Temperature dependent measurements of ΔT in Gadolinium and LaFeSi between 270 and 310 K exhibit maxima close to their Curie temperatures as expected for the MCE. The high sensitivity of our new approach (few mK) allows for the first time to verify in the low field range of Gadolinium a quadratic dependence of the temperature change on the magnetic field.