An AC technique to directly measure magnetic field induced adiabatic temperature change

Because magnetic refrigeration might become an attractive alternative to conventional compression refrigeration, there is growing interest in studying equilibrium and AC aspects of the Magneto-Caloric Effect (MCE). We present a dynamic and direct measurement of adiabatic temperature change and compare it with the conventional but indirect DC magnetometric approach utilizing Maxwell’s relation. We use far infra-red detection technique to measure the periodic change in temperature in the archetypical magnetocaloric Gadolinium caused by the application of a low frequency AC magnetic field. For comparison we use SQUID magnetometry to determine isothermal entropy and adiabatic temperature change. The AC method provides additional information about the magnetic properties of the magnetocaloric material such as the temperature dependence of the low frequency magnetic susceptibility. In addition it reveals non-equilibrium effects which are relevant when applying the MCE in a cycling cooling device.