Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes

Yoann Prado (1) , Niéli Daffé (1, 2, 3) , Aude Michel (1) , Thomas Georgelin (4) , Nader Yaacoub (5) , Jean-Marc Greneche (5) , Fadi Choueikani (3) , Edwige Otero (3) , Philippe Ohresser (3) , Marie-Anne Arrio (2) , C. Cartier Dit Moulin (6) , Ph. Sainctavit (2, 3) , Benoit Fleury (6) , Vincent Dupuis (1) , Laurent Lisnard (6) , Jérôme Fresnais (1)

1 PHENIX - PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX
2 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
3 SSOLEIL - Synchrotron SOLEIL
4 LRS - Laboratoire de Réactivité de Surface
5 IMMM - Institut des Molécules et Matériaux du Mans
6 IPCM - Institut Parisien de Chimie Moléculaire

Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest—and more attractive—systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5nm g-Fe₂O₃ nanoparticles with the [Co^II(TPMA)Cl₂] complex (TPMA: tris(2- pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination—without nanoparticle aggregation and without complex dissociation—of the molecular complexes to the nano- particles surface. Magnetic measurements indicate the significant enhancement of the ani- sotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude.

Domains: Chemical Sciences; Physics [physics]

Yoann Prado, Niéli Daffé, Aude Michel, Thomas Georgelin, Nader Yaacoub, et al.. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes. Nature Communications, 2015, 6, pp.10139. ⟨10.1038/ncomms10139⟩. ⟨hal-01390543⟩