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Magnetotransport and ferromagnetism in thin films of Co2Si nanoclusters are investigated experimentally and theoretically. The nanoclusters are fabricated by an inert-gas condensation-type cluster-deposition method and have an average size of 11.3 nm. Unlike the bulk Co2Si that exhibits a very weak net magnetic moment only below 10 K, the nanoclusters exhibit room-temperature ferromagnetism with a substantial saturation magnetization. Key features of the system are its closeness to the Stoner transition, magnetic moments induced by spin polarization starting from surface atoms, and nonuniaxial anisotropy associated with the orthorhombic crystal structure of Co2Si. A method is introduced to determine the effective anisotropy using the experimental magnetization data of this complex system and its relationship with the two lowest-order nonuniaxial anisotropy constants. On decreasing temperature from 300 K, the nanoclusters show electron-transport properties unusual for a ferromagnetic metal, including an increase of Hall resistivity and a nonmonotonic change of negative magnetoresistance with a peak at around 100 K. The underlying physics is explained on the basis of the large polarization of surface spins and variation in the degree of their misalignments due to temperature-dependent effective anisotropy. 

The structural, magnetic and magnetocaloric properties of Fe deficient Pr2-xNdxFe17 (x = 0.5, 0.7) alloys prepared by arc-melting and melt-spinning have been investigated. The room temperature x-ray diffraction patterns show that the samples are nearly single-phase and crystallize in the rhombohedral Th2Zn17-type crystal structure. The Curie temperatures determined from the thermomagnetic curves are 302 K and 307 K for Pr1.5Nd0.5Fe17 and Pr1.3Nd0.7Fe17, respectively. The peak magnetic entropy change and the relative cooling power at field change of 50 kOe are 3.01 J/kgK and 345 J/kg for Pr1.5Nd0.5Fe17, and 4.31 J/kgK and 487 J/kg for Pr1.3Nd0.7Fe17, respectively. The absence of magnetic and thermal hysteresis with relatively high cooling efficiency suggests that the alloys have potential for magnetic refrigeration.