The Magnetocaloric Effect Of Lafe_(11.6)si_(1.4), La_(0.8)nd_(0.2)fe_(11.5)si_(1.5), And Ni_(43)mn_(46)sn_(11) Compounds In The Vicinity Of The First-order Phase Transition

摘要

The magnetocaloric effect (MCE), found by Warburg, provides a unique way for realizing refrigeration from ultralow temperatures to room temperature. With an increase of applied field, the magnetic entropy decreases and heat is emitted from the magnetic system to the environment in an isothermal process; with a decrease of applied field, the magnetic entropy increases and heat is absorbed from the lattice system to the magnetic system in an adiabatic process. Both the large, isothermal entropy change and the adiabatic temperature change characterize the prominent MCE. Over the past few years, the MCE and magnetic refrigeration materials have been investigated extensively, and several kinds of magnetic-refrigerant prototype instruments have been implemented experimentally. However, the origin and evaluation method of the MCE are still in dispute. Here, we will start from the thermodynamic deduction, then combine magnetic and caloric measurements to study the MCE in the vicinity of the first-order phase transition.