Influence of the crystalline electrical field on the magnetocaloric effect of DyAl2, ErAl2, and DyNi2

Calculations of the magnetic entropy change Delta S-mag and the magnetocaloric effect (i.e., the adiabatic temperature change) Delta T-ad in DyAl2, ErAl2, and DyNi2 using a Hamiltonian that takes into account the effects of crystalline electrical field and exchange interaction have been carried out. Good agreement between the theory and the experiment was obtained using the crystal-field parameters from inelastic neutron scattering for DyAl2 and ErAl2. The crystal-field parameters for DyNi2, which were reported from magnetization measurements, did not give good agreement between the theory and the experiment. Using the experimental Delta S-mag versus T, and C-mag versus T (where C-mag is the magnetic heat capacity) we made an estimate of the crystal-field parameters for DyNi2, which yield a satisfactory agreement between the theory and the experiment with regard to Delta S-mag and Delta T-ad The appearance of a hump in the theoretical Delta S-mag(T) below the Curie temperature is discussed. [S0163-1829(98)05642-2].