Time: 05:00 p.m.
Place: Materials Day 2013, Ruhr-Universität Bochum, Bochum, Germany
Daniel Hägele, Experimentalphysik, Ruhr-Universität Bochum, Bochum, Germany
The change in temperature of a material in a magnetic field is called the magnetocaloric effect. Materials with large magnetocaloric effects bear prospects for the construction of energy efficient cooling devices. A desired systematic investigation of materials with varying element compositions requires a method to measure temperature changes in small volume samples or even thin films. This excludes traditional calorimetry which requires samples in the mm-range. Here, we present a new approach that is based on measuring thermal radiation of small samples in a magnetic field that is modulated with frequencies beyond 30 Hz. The high sensitivity of the approach 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. At higher fields we find a transition to the usual linear dependence known from traditional calorimetry.