Nanomagnetism study of highly-ordered iron oxide nanocrystal assemblies fabricated by the Langmuir–Blodgett technique

Enhanced Collective Magnetic Properties in 2D Monolayers of Iron Oxide Nanoparticles Favored by Local Order and Local 1D Shape Anisotropy

“…23 However, multilayer assemblies which involve a larger number of interacting nanoparticles favor stronger dipolar interactions and better stability against external magnetic fields. 17,19,20,24 Another approach, the Layer-by-Layer technique was also used to prepare multilayered hierarchical assemblies. 10,25 The increase of the interlayer distance favored in-plane dipolar interactions within layers and their antiparallel coupling.…”

“…Highly structured assemblies of nanoparticles supported onto substrates can be prepared following bottom-up strategies. ,, These techniques are mainly based on the stability of non aggregated nanoparticles in solvents as well as the design of surface functionalities on both substrates and nanoparticles. The Langmuir–Blodgett (LB) technique is certainly one of the most popular way to prepare well-defined assemblies of magnetic nanoparticles as monolayers and multilayers. − The precise control on the dimensionality of assemblies has highlighted the strong influence of 2D shape anisotropy on the collective magnetic properties. ,,, The orientation of magnetic moments is favored in-plane which enhances dipolar interactions in comparison to 3D random assemblies such as powders. Furthermore, anisotropic and strong dipolar interactions in monolayer raised up collective properties to superferromagnetism .…”

“…The modulation of the size of ligands grafted at the surface of nanoparticles also enabled us to tune dipolar interactions as a function of the interparticle distance . However, multilayer assemblies which involve a larger number of interacting nanoparticles favor stronger dipolar interactions and better stability against external magnetic fields. ,,, Another approach, the Layer-by-Layer technique was also used to prepare multilayered hierarchical assemblies. , The increase of the interlayer distance favored in-plane dipolar interactions within layers and their antiparallel coupling . More recently, unidirectional shape anisotropy has been also reported in pyramidal assemblies of cobalt ferrite nanoparticles …”

Effect of Disorder and Dipolar Interactions in Two-Dimensional Assemblies of Iron-Oxide Magnetic Nanoparticles

“…On the other hand, the preparation of two-dimensional (2D) assemblies, such as monolayers with high topographical control, is well established. , In contrast to random assemblies such as powder, collective properties have been reported to be markedly enhanced by the shape anisotropy, which favors in-plane dipolar interactions. − The preparation of NP monolayers by the Langmuir–Blodgett technique with tunable interparticle distance (1–10 nm) confirmed that the blocking temperature behaves as a –3 , where a is the interparticle distance . This scaling of the blocking temperature was also observed in solvents .…”