A layer structural complex magnetic refrigerant, which is suitable for the Ericsson cycle, satisfying the Carnot principle, has been investigated. Above ∼15 K, since the thermal agitation energy and the lattice entropy increase considerably, the ferromagnetic material has to be used for the refrigerant in the magnetic refrigeration. However, the variatio of the magnetic entropy of the ferromagnets is not ap propriate to the Ericsson cycle in which the entropy difference ΔSJ between two kinds of the iso-magnetic field processes should be constant in the refrigeration range. In order to make the refrigerant having constant ΔSJ mentioned above, we made the layer structural sin tered material composed of four kinds of ferromagnets ErAl2.2, HoAl2.2, (DY0.5Ho0.5)Al2.2 and DyAl2.2, and investigated its entropy experimentally. As the result, it is verified that the layer structural magnet material is one of the most promising refrigerant for the Ericsson cycle.
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