  The entropy and cooling rate of the both antiferromagnetic spin-1/2 double
sawtooth IsingHeisenberg model and mixed-spin (1,1/2) double sawtooth
Ising-Heisenberg model on the distorted ladders are rigorously investigated
under an adiabatic demagnetization process using the quantum transfer-matrix
technique. The models include the XXZ interaction between the interstitial
Heisenberg dimers, the Ising coupling between nearest-neighbor spins of the
legs and rungs, and additional cyclic four-spin exchange (ring exchange) in the
square plaquette of each block. Close to field-induced quantum phase
transitions, we compare both models together in the ability of cooling/heating
near the quantum critical points. However, we observe a large magnetocaloric
effect for both models, the mixed-spin double sawtooth ladder shows much more
magneticaloric efficiency than the spin-1/2 double sawtooth ladder. During an
adiabatic demagnetization process it can be seen a temperature dropping in the
vicinity of the zero-temperature quantum phase transitions. Various fixed
values of the Isotropic and anisotropic parameters explicitly alter the quality
of the magnetocaloric effect. This properties suggest double sawtooth
Ising-Heisenberg ladders as promising alternative refrigerant materials for
low-temperature magnetic refrigeration.
