Magnetic refrigeration materials

Various types of work in addition to pV work are frequently involved in experimental studies. Research on chemical equilibria for example may involve surfaces or phases at different electric or magnetic potentials [11], We will here look briefly at field-induced transitions, a topic of considerable interest in materials science. Examples are stress-induced formation of piezoelectric phases, electric polarization-induced formation of dielectrica and field-induced order-disorder transitions, such as for environmentally friendly magnetic refrigeration. 

Dysprosium 66 Dy Catalysts, electronic materials, phosphor activators, magnetic refrigeration, magnetostrictive alloys... 

Since the input and output can be interchanged in a symmetrical three dimensional transducer, this interchange principle can be effectively used in magnetic refrigeration. The operating temperature range determines the working material and the Gd Metal is most suitable for ambient conditions. 

Recently, a new liquefaction approach based on the magnetocaloric effect has been proposed [115]. The method is based on the characteristics of some magnetic materials that heat up when placed in a magnetic held and cool down when removed from it. The magnetic refrigeration can develop its potentialities in terms of overall efficiency for liquefaction process, as it is theoretically able to exploit... 

Figure 9.13 shows the temperature dependence of —ASm for fioAH = 2 T for type-1 and type-VIII EugGaieGeso and for type-I Eu4Sr4Gai6Ge3o, calculated from the M(H) isotherms in Figs. 9.8 and 9.9 (left), using Eq. 9.9. For comparison, ASm of EuO, one of the best candidate materials for magnetic refrigeration at 70 K [53], is also given in Fig. 9.13. The four materials exhibit peaks at their respective Curie temperatures (Fig. 9.13).

Another important practical parameter to measure in magnetic refrigeration is the adiabatic temperature drop in K. Actually, if H is changed in such way that the specific entropy of the material S, in J.kg K , remains constant, and if the state of the substance is always in thermal equihbrium in the magnetic field H, then the absolute temperature of the material, T, in K, will change according to the following equation ... 

These formulas indicate that fine-particle materials can be used for magnetic refrigeration for temperatures well in excess of the present maximum of 20 This is demonstrated by the results obtained on... 

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