Magnetocaloric effect in kinetically frustrated diamond chains

Abstract

We investigate the magnetocaloric effect in a diamond chain model on which competing interactions result from the local quantum hopping of interstitial $S=1/2$ spins which are intercalated between nodal Ising spins. The model is exactly solvable by using exact diagonalization and the decoration-iteration mapping onto the one-dimensional Ising model with effective parameters depending on the temperature and the external magnetic field. We analyze the thermodynamic behavior of the effective parameters in light of the ground-state ordering and the level crossing of the low-lying excited states. Further, we investigate the magnetocaloric effect on this spin chain model by computing isoentropy curves in the temperature versus external field parameter space, as well as the adiabatic cooling rate. We show that the adiabatic cooling rate exhibits a pronounced valley-peak structure in the vicinity of the critical fields associated with zero-temperature phase transitions.