Demagnetization experiments on some promising new compounds for very low-temperature refrigeration

We have performed demagnetization experiments on spherical specimens of silver chloride-bonded, compacted powders of four different compounds. Pure and lanthanum-diluted cerium magnesium nitrate (CMN) was studied along with two new compounds formed from cerium iodide and antipyrine and from cerium thiocyanate and triphenyl phosphine oxide. The magnetic temperatures T* were determined from measurements of the magnetic susceptibility perpendicular to the axis of the initial magnetizing field. Both the lanthanum-diluted CMN and the triphenyl phosphine oxide compounds yielded significantly lower values of T* than that obtained with CMN. The problem of thermal equilibrium within the demagnetized sample is considered.