Elaboration of mesostructures based on magnetic nanocrystals: modulation of dipolar interactions from super-ferromagnetism to magnetic decorellation

International audienceIn an assembly of highly concentrated magnetic nanoparticles (NPs), the materials’ magnetic properties can be greatly influenced by their mutual dipolar interactions. In particular, the existence of a long-range ordered state where their individual magnetic moments are aligned ferromagnetically (dipolar superferromagnetic state, SFM) is predicted [1]. However, a clear-cut experimental evidence of it in real 3D NP assemblies has so far remained elusive. This is most likely due to the stringent geometrical/physical conditions required for inducing a dipolar SFM state. In this context, we intend to produce a dipolar SFM state in columnar supercrystals of dodecanoic acid coated Co NPs. This presentation focuses on the synthesis and characterizations of Co nanoparticles [2] and in the elaboration of mesostructures (labyrinths, voids and columns) obtained by the evaporation of a colloidal solution under an external magnetic field [3,4].(1) Majetich, S. A.; Sachan, M. J. Phys. Appl. Phys. 2006, 39 (21), R407.(2) Lisiecki, I.; Pileni, M. P. Langmuir 2003, 19 (22), 9486.(3) Salzemann, C.; Richardi, J.; Lisiecki, I.; Weis, J.-J.; Pileni, M. P. Phys. Rev. Lett. 2009, 102 (14).(4) Germain, V.; Richardi, J.; Ingert, D.; Pileni, M. P. J. Phys. Chem. B 2005, 109 (12), 5541