Erbium-doped yttrium aluminum garnet as a magnetic refrigerant for low temperature x-ray detectors

Based on the measurements of specific heat and magnetization, the Er(super 3+)-doped yttrium aluminum garnet (YAG) has been shown as suitable for a magnetic refrigerant in adiabatic demagnetization refrigerators (ADRs) working at a temperature ~100 mK. The two important properties of YAG are the relation between the doping fraction of Er(super 3+) and the deltaS(sub M) value and the variation of heat conductivity with the doping fraction.