Controlling of magnetocaloric effect in Gd2O3@SiO2 nanocomposites by substrate dimensionality and particles’ concentration

The magnetocaloric effect (MCE) of hybrid nanostructures consisting of fine gadolinium oxide (Gd2O3) nanoparticles with diameter 7 nm and 12 nm loaded into the pores of the periodically ordered mesoporous silica with hexagonal (SBA-15) or cubic (SBA-16) symmetry were investigated. The concentration effect of the added nanoparticles (NPs) and the effect of the silica matrix dimensionality on the structural properties, magnetization M(H), magnetic entropy change ΔS M , and parameters A(T) and B(T) derived from Arrott plots were studied in four samples. Examined nanocomposites exhibited reasonable high values of magnetic entropy change ΔS M varying from 29 J/kgK established for Gd2O3@SBA-15 up to 64 J/kgK observed in Gd2O3@SBA-16 at maximal field change 5 T at low temperatures. This suggests that studied nanocomposites, where diamagnetic silica matrices serve as nanoreactors for growth of Gd2O3 nanoparticles and their symmetry strongly affect magnetic properties of whole composites, could be feasible for cryomagnetic refrigeration applications.