Magnetocaloric Effect in Magnetic Nanoparticle Systems: How to Choose the Best Magnetic Material?

Magnetic nanoparticles with controlled magnetocaloric properties are a good candidate to lower the temperature of nanosized systems: they are easy to manipulate and to distribute into different geometries, as wires or planes. Using a Monte Carlo technique we study the entropy change and refrigerant capacity of an assembly of fine magnetic particles as a function of their anisotropy and magnetization, key-parameters of the magnetic behavior of the system. We focus our attention on the anisotropy energy/dipolar energy ratio by means of the related parameter c(0) = 2K/M(S)(2), where K is the anisotropy constant and M(S) is the saturation magnetization of the nanoparticles. Making to vary the value of c(0) parameter by choosing different K-M(S) combinations, allows us to discuss how the magnetocaloric response of an assembly of magnetic nanoparticles may be tuned by an appropriate choice of the magnetic material composition.