Magnetocaloric Effect and Giant Dissipative Heating in Dysprosium in Alternating Magnetic Fields

The magnetocaloric effect and dissipative heating in a polycrystalline dysprosium sample in alternating magnetic fields have been studied by direct measurements. It has been shown that the maximum adiabatic temperature change is about 1.5 K at a field amplitude of 1.2 T. At the same time, giant irreversible heating has been observed in the region of the antiferromagnetic phase: the temperature difference between the sample and the thermostat exceeds 50 K and significantly depends on the field frequency and the initial temperature of the sample. This effect cannot be explained by eddy currents or the conventional hysteresis losses characteristic of ferromagnets. The observed energy dissipation has been attributed to the irreversible motion of the helical domain walls in the antiferromagnetic phase, which has already been predicted theoretically, but has not yet been confirmed experimentally in quantitative form.