Cited research: Phys. Rev. Lett. 104, 207203 (2010)

Experimental findings confirm a theoretical prediction that certain chemically uniform nanoparticles have magnetically distinct cores and shells.

Using refined neutron-scattering techniques, Kathryn Krycka of the National Institute of Standards and Technology in Gaithersburg, Maryland, and her team probed the three-dimensional magnetic structure of magnetite nanoparticles nine nanometres wide. In the presence of an external magnetic field, they found a shell layer 1.0–1.5 nanometres thick in which magnetization was angled at 90° to the particle's core.

The findings indicate that nanoparticles cannot be assumed to have uniform magnetic moments — which could be useful in applications such as data storage. D.P.C.