| In an effort to show that the magnetothermal properties of a material can be varied in a manner useful for magnetic refrigeration, Gd doped EuS has been synthesized using an arc melting technique and its magnetic heat capacity measured. The heat capacity data shows little change from pure EuS, probably due to compensation of the donor electrons caused by inhomogeneous doping.;Also a figure of merit has been developed to evaluate the effort required, due to the intrinsic properties of the materials, to implement a given refrigeration cycle. On the basis of this figure of merit a simple scaling argument indicates that a refrigeration cycle using active magnetic regeneration would be better than a single stage, passively regenerated cycle when the temperature span is greater than the heat source temperature. In addition, an analysis of an idealized Ericsson cycle using active magnetic regeneration is made and a technique to match the fixed temperature ends to the regenerator temperature variation is developed that shows qualitative new features not previously recognized.;Analysis of the data in terms of its refrigerant capacity and comparison to mean field calculations indicate that EuS is a more effective refrigerant in the 4-35 K region than Gd... |
