Magnetic Cooling and Phase Transition in Spin Pair System, CeCl₃.7H₂O

Abstract

The magnetic cooling and phase transition are studied experimentally in the spin pair system with the singlet ground state, CeCl₃.7H₂O. The results of the successful adiabatic demagnetization of CeCl₃.7H₂O from the initial condition, H_i=48 kOe and T_i=1.2 K, are reported. The cooling curve is obtained with the minimum temperature of 68 mK around the energy level crossing field of 4.7 kOe. The susceptibility at the crossing field is represented by the Curie-Weiss law with the ferromagnetic Curie-Weiss temperature of 68 mK in sufficiently low temperature region. The bottom of the cooling curve becomes flat around the crossing field at the temperature below 72 mK. It is concluded that the spin ordering occurs around the crossing field at the temperatures lower than the critical temperature of 72 mK.