SANS

Small-angle neutron scattering (SANS) will give information of the individual single-core crystal sizes as well as sizes of clusters of single-core crystals. The technique can also give information on the whole particle size and structure/shape including the coating material, if deuterated solvents or coating materials are used. These techniques, as those for some X-ray techniques, are housed in Large-Facilites, usually of European (global) character (RAL-ISIS, ILL,), but also in local sources such as LLB (France), HMI (Germany), etc. Consequently we will depend on the allocation of beam time by the corresponding scientific panel. As commented above for the X-ray scattering case, we count with two very powerful and complementary techniques here.

It is well-known that in the case of neutron scattering there exits the possibility of extracting the magnetic contribution of the nanoparticle ensembles. Thus, we will be able to extract such a contribution, especially if the particles present an antiferromagnetic/ferrimagnetic core with an order temperature below RT. In ferromagnetic nanoparticles the signal will add coherently to the nuclear peaks. These data must be collected in neutron sources and fortunately we may use several top-end sources in Europe. In some cases, we will need to use high-flux instruments for neutron diffraction (ND) such as, for example, D20 at the Inst. Laue-Langevin. The patterns will be analyzed by magnetic Rietveld refinement mainly using FULLPROF. From the patterns the same parameters described for the X-ray diffraction can be extracted. In fact multipattern Rietveld can be performed using sets of data from different X-ray and neutron instruments, and eventually backed up by the aid of EXAFS/XANES. This enables an extremely precise evaluation of the arrangement of the collection of particles. In such ND experiments we can also observe the eventual increase of low-angle scattering, which eventually would be a sign of single/multicore structures. The time collection is variable but a batch of samples can be measured in 2 days. Equally important will be the data extracted from the Small-Angle Neutron scattering (SANS): this technique allows the characterization in the range 1-150 nm (selecting the appropriate Q-range). The SANS spectra can provide the average size, size distribution and spatial correlation. For this one should get the differential cross section, which may include a magnetic contribution; we will need to apply magnetic fields and temperature variation which allow to decouple the nuclear and magnetic signals and also to scrutinize the low-field evolution of the magnetic signal. There is a problem related with the amount of sample and the poly-dispersity but we will establish routines to use series of samples with different volume fraction of particles and number of multicore particles to establish tendencies of the parameters. High-flux instruments such as SANS2D or D22 might be then required. Other examples of particle systems including ferrofluids and Nanoperm have been analysed with polarized neutrons, allowing to extract the core-shell structure and work below the magnetic order temperature. This core-shell structure is different in single-core and multi-core structures. In summary given a series of particles with different sizes and inter-particle distances there is an excellent opportunity to establish the SANS/SAXS use. These techniques, as those for some X-ray techniques, are housed in Large-Facilites, usually of European (global) character (RAL-ISIS, ILL,), but also in local sources (access partially granted via EU support) such as LLB (France), HMI (Germany), etc.

Project Partners

Project partners


	This project has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 604448