%0 Journal Article %T Beyond Entropy: Magnetic Forces Induce Formation of Quasicrystalline Structure in Binary Nanocrystal Superlattices %+ De la Molécule aux Nanos-objets : Réactivité, Interactions et Spectroscopies (MONARIS) %+ Service de physique de l'état condensé (SPEC - UMR3680) %A Yang, Zhijie %A Weig, Jingjing %A Bonville, Pierre %< avec comité de lecture %@ 0002-7863 %J Journal of the American Chemical Society %I American Chemical Society %V 137 %N 13 %P 4487–4493 %8 2015 %D 2015 %R 10.1021/jacs.5b00332 %Z Physics [physics]Journal articles %X Here, it is shown that binary superlattices of Co/Ag nanocrystals with the same size, surface coating, differing by their type of crystallinity are governed by Co–Co magnetic interactions. By using 9 nm amorphous-phase Co nanocrystals and 4 nm polycrystalline Ag nanocrystals at 25 °C, triangle-shaped NaCl-type binary nanocrystal superlattices are produced driven by the entropic force, maximizing the packing density. By contrast, using ferromagnetic 9 nm single domain (hcp) Co nanocrystals instead of amorphous-phase Co, dodecagonal quasicrystalline order is obtained, together with less-packed phases such as the CoAg13 (NaZn13-type), CoAg (AuCu-type), and CoAg3 (AuCu3-type) structures. On increasing temperature to 65 °C, 9 nm hcp Co nanocrystals become superparamagnetic, and the system yields the CoAg3 (AuCu3-type) and CoAg2 (AlB2-type) structures, as observed with 9 nm amorphous Co nanocrystals. Furthermore, by decreasing the Co nanocrystal size from 9 to 7 nm, stable AlB2-type binary nanocrystal superlattices are produced, which remain independent of the crystallinity of Co nanocrystals with the superparamagnetic state. %G English %L cea-01365887 %U https://cea.hal.science/cea-01365887 %~ CEA %~ UPMC %~ CNRS %~ MONARIS %~ INC-CNRS %~ IRAMIS-SPEC %~ CEA-UPSAY %~ UNIV-PARIS-SACLAY %~ CEA-UPSAY-SACLAY %~ UPMC_POLE_2 %~ SORBONNE-UNIVERSITE %~ SU-SCIENCES %~ IRAMIS %~ GS-PHYSIQUE %~ INSTITUT-SCIENCES-LUMIERE %~ ALLIANCE-SU %~ TEST2-HALCNRS %~ CHIMIE-SU