A new criterion to distinguish the order of magnetic transitions by means of magnetic measurements

摘要

A universal curve for the magnetic entropy change has been found to exist for a variety of materials with second order phase transitions. We have studied whether this universal behavior of the magnetocaloric effect is maintained in materials with first order phase transition, including RCo_2 Laves phases and mixed La_(2/3)(Ca_xSr_(1-x))_(1/3)MnO_3 manganites, which present both second order and first order magnetic ordering phase transitions. The rescaled magnetic entropy change curves for different applied fields collapse onto a single curve only for materials with second order phase transition. This universal curve may be used as a criterion for determining the order of magnetic phase transitions from purely magnetic measurements.