Magnetocaloric Materials for Freezing, Cooling, and Heat-Pump Applications - Magnetocaloric Energy Conversion: From Theory to Applications - page 24

temperature. Nowadays, a lot of effort is put into the research and design of
magnetocaloric devices; however, even more effort is directed at the research of
new MCMs that would be suitable for use in near-room-temperature applications.
There are a number of different MCMs available for use near room temperature;
these are thoroughly described in various reviews in the literature [ 23

28 ]. Fur-
thermore, there is also a topic written by Tishin and Spichkin [ 29 ] which describes
numerous different MCMs in details.
In general, MCMs can be divided into two groups based on the order of their
phase transition from the ferromagnetic to paramagnetic state, thus calling them
second-order or

-

rst-order materials [ 30 ]. The phase transition happens at the
certain temperature, referred to as the Curie temperature. Above the Curie tem-
perature the spontaneous magnetization disappears and the material becomes
paramagnetic. Furthermore, the MCE is most noticeable at this phase transition.
The difference between

rst-order and second-order materials is how this transition

takes place (Fig. 2.1 ).

Fig. 2.1 Schematic general distinctions between second-order and rst-order materials via
magnetization (a and b) and specic heat (c and d) in relation to temperature and magnetic eld