NOVEL THERMAL EFFECTS AT THE FIRST-ORDER MAGNETIC PHASE-TRANSITION INERBIUM, AND A COMPARISON WITH DYSPROSIUM

In low temperature studies of ultrapure erbium (and dysprosium) we hav e discovered unusual thermal effects at the first order magnetic trans formation of erbium (congruent to 19 K). These include (1) superheatin g (i.e., the metal is colder after heat has been added to it than befo re the heat pulse), (2) supercooling, and (3) the existence of metasta ble intermediate phases during this phase transformation in erbium (fo ur on heating and two on cooling). In comparison, dysprosium exhibits both superheating and supercooling, but no intermediate metastable pha ses are observed. Furthermore, none of these effects are observed in l ess pure metals.