Pulsed thermo-magnetic effects in rare earth compounds

A pulsed, tuneable dye laser has been used to pump the optical energy levels of single crystals of rare earth compounds. Because of the short relaxation times, this results in fast heating of the crystals. The subsequent changes in magnetization have been recorded and explained using the known magnetic properties. The slow cooling is exponential provided the heat pulses are small and is limited by the kapitza boundary resistance (varying as t-3) when the helium is superfluid. In normal helium the thermal resistance also varies as t-3. Large heat pulses give anomalous magnetic signals, with very long delay times, and these are interpreted in terms of the formation of a gas film around the crystal surface.