MONTE-CARLO SIMULATIONS OF THE MAGNETOCALORIC EFFECT IN SUPERFERROMAGNETIC CLUSTERS HAVING UNIAXIAL MAGNETIC-ANISOTROPY

The magnetic entropy change, DELTAS (hence the heating or cooling) of ferromagnetically coupled magnetic clusters induced by an application of a magnetic field is substantial and occurs over a broad temperature range. This behavior contrasts with a ferromagnetic material, where l arger entropy changes can be obtained, but only over small temperature ranges close to the Curie point. Monte Carlo simulations have been ca rried out to obtain DELTAS when the spins are subjected to uniaxial an isotropy fields. While previous calculations for interacting spins sho wed increases in the Curie temperature and enhancements of DELTAS in t he vicinity of the Curie point with increasing anisotropy, the present results for interacting clusters show similar increases in the temper ature of DELTAS peaks accompanied by decreases in the peak values of D ELTAS. These results show that the flattening of the DELTAS peaks, whi ch make superferromagnetic materials valuable for magnetic refrigerati on is assisted by the presence of uniaxial anisotropy. Some effects on DELTAS of placing the spins on fixed BCC, FCC, and sc lattices are re ported.