  The magnetic and magnetocaloric properties of the mixed spin-(1/2,1)
Ising-Heisenberg model on a two-leg ladder with dimer-rung alternation are
exactly examined under an adiabatic demagnetization process using the
transfer-matrix formalism. We notify that the magnetization curve of the model
exhibits plateaux as a function of the applied magnetic field and cyclic
four-spin Ising interaction at certain rational fractions of the saturation
value. We precisely investigate the ability of cooling/heating of the model
nearby the critical points at which discontinuous ground-state phase transition
occurs. It is evidenced that the model manifests an enhanced magnetocaloric
effect in a proximity of the magnetization steps and jumps, accompanying with
the plateaux and jumps of correlation function of the dimer spins. We conclude
that not only the cooling/heating capability of the model could be pleasantly
demonstrated by the applied magnetic field variations, but also a typical
cyclic four-spin Ising interaction plays essential role to determine an
efficiency of the magnetocaloric effect of the model.
