The system RNi2 (R: rare earth heavy metals, Dy, Er) is proposed as the regenerative material. We prepared the solid solution of this system and measured the temperature variation of the specific heat up to 5 T. This system has a large specific heat below 20 K due to ferro to paramagnetic transition. The Curie temperature can be controlled by changing the composition of the rare earth elements. The entropy is evaluated and it is made clear that this system is also applicable to the refrigerant in an Ericsson cooling cycle.
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