Giant enhancement and anomalous temperature dependence of magnetism in monodispersed NiPt2 nanoparticles
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A simple yet general one-step solvothermal method is applied to synthesize sub-7 nm monodispersed single-crystal NiPt2 nanoparticles (NPs) with the morphology of truncated octahedrons in the alloying state of disordered atomic arrangements. The effective magnetic moments of these NPs exhibit an anomalous temperature dependency, increasing from approximately 0.9 μB/atom at 15 K to 1.9 μB/atom at 300 K. This is an increase by a factor of more than three compared with bulk Ni. On the basis of experiments involving X-ray absorption near-edge spectroscopy of the L3 edge for Pt and density functional theory calculations, the observed novel magnetism enhancement and its anomalous temperature dependence are attributed to the electron transfer arising from the thermal-activation effects.
KeywordsNiPt2 nanoparticles magnetism X-ray absorption near-edge spectroscopy density functional theory calculations
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Authors acknowledge Dr. Lirong Zheng for his XANES experimental support at the XAFS station in 1W1B beamline of BSRF and useful discussion. This work is supported by the National Natural Science Foundation of China (Nos. 11674008, 11674023, 21576008, 91334203, 51371015 and 51331002), the Beijing Natural Science Foundation (No. 2142018) and Beijing Municipal Science and Technology Project (No. Z17111000220000).
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