The influence of the quadrupolar interaction in the magnetocaloric effect

Using a model Hamiltonian, which takes into account the dipolar and quadrup olar interaction within the molecular field approximation, it was possible to investigate the influence of a magnetic phase transition on the magnetoc aloric potential. The results obtained show that discontinuous changes in t he order parameters associated with the first-order phase transition involv e a strong enhancement in magnetocaloric potential (which has practical imp ortance for magnetic refrigeration efficiency) at the critical temperature. These results were fully discussed and correlated with the Maxwell thermod ynamic relations. (C) 2000 Elsevier Science Ltd. All rights reserved.