A novel principle for cooling by adiabatic pressure application in the mixed crystalline compoundPr1−xLaxNiO3is described and experimentally verified. Cooling occurs in the vicinity of the structural phase transition where the electronic ground state of thePr3+ions changes from a singlet to a doublet state. By properly choosing the La concentrationx, the cooling effect can be achieved down to some 100 mK. Furthermore,Pr1−xLaxNiO3can be used for second and third stage cooling down to the &mgr;K region by classical paramagnetic and nuclear demagnetization techniques, respectively. ©1998 American Institute of Physics.