Nanomagnetic particles can have properties and useful functionality that is quite different from the same materials in the bulk. Chemical synthesis can be used to control the size, shape and dispersity of nanoparticles, while modification of the surface can greatly modify their magnetic properties. Surface functionalisation can also be used to induce self-organisation or to refine the nanoparticle properties for different applications. Such particles have a range of potential applications, ranging from magnetic storage and sensors through to biological assays and directed drug delivery.

In addition to the work we have undertaken on nanomagnetic materials specifically intended for application in magnetic recording media, we are also currently involved with a number of groups in the UK, Japan, Korea and France to explore the fabrication, properties and applications of nanoparticles produced via nanocolloidal synthesis. These routes can lead to particles with very narrow size distributions and a well defined particle separation in the as-deposited state. Particle diameters as small as 2 nm can be produced with a size dispersion of only 5%.

We are also working with the group of Professor Laura Heydermann at the ETH, Zurich to explore the collective properties of interacting arrays of artificially arranged and controlled nanoparticles produced using electon beam lithography. An example of this is our recent exploration of spin ice physics using artificial nanomagnetic arrays.

Artificial array of nanomagnetic island in a Kagome spin-ice configuration. The fluctuating and interacting dipoles exhibit the phase transitions shown schematically on the right (article).

Selected Publications

Dynamical Torque in Co_xFe₃O₄ Nanocube Thin Films Characterized by Femtosecond Magneto-Optics: A Pi-Shift Control of the Magnetization Precession,
Mircea Vomir,Robin Turnbull, Ipek Birced, Pedro Parreira, Donald A. MacLaren, Stephen L. Lee, Pascal Andre, and Jean-Yves Bigot
NanoLetters (July 2016) DOI: 10.1021/acs.nanolett.6b02618.

Silicide induced surface defects in FePt nanoparticle fcc-to-fct thermally activated phase transition,
Shu Chen, Stephen L. Lee, Pascal Andre,
Journal of Magnetism and Magnetic Materials, 417 442-450 (2016).

Thermodynamic phase transitions in a frustrated magnetic metamaterial,
L. Anghinolfi , H. Luetkens, J. Perron, M.G. Flokstra, O. Sendetskyi, A. Suter, T. Prokscha, P.M. Derlet, S.L. Lee, L.J. Heyderman,
Nat. Commun., 6 8278(6) (2015).

Inhomogeneous composition of alloyed iron-platinum magnetic nanoparticles synthesized at low temperature Chen, S., MacLaren, D. A., Baker, R. T., Chapman,
J. N., Lee, S., Cole-Hamilton, D. J. and Andre, P., Journal of Materials Chemistry
21(11) 3646-3654 (2011).

Inhomogeneous composition of alloyed iron-platinum magnetic nanoparticles synthesized at low temperature
Shu Chen, Donald A. MacLaren, Richard T. Baker, John N. Chapman, Stephen Lee, David J. Cole-Hamilton and Pascal Andre
Journal of Materials Chemistry 21(11) 3646-3654 (2010).

Engineered Biocompatible Nanoparticles for in Vivo Imaging Applications
Chen, S., Wang, L., Duce, S. L., Brown, S., Lee, S., Melzer, A., Cuschieri, S. A. and Andre, P.
Journal of the American Chemical Society 132(42) 15022-15029 (2010).

Agglomeration and sintering in annelaed FePt nanoparticle assemblies studied by small angle neutron scattering and X-ray diffraction.
Thomson, T. and Lee, S.L.,
PRB 72 (6): Art. No. 064441, 2005.

Structural and magnetic model of self-assembled FePt nanoparticle arrays.
T.Thomson, M.F. Toney, S. Raoux, S. L. Lee, S. Sun, C.B. Murray, B.D.Terris,
J. Appl. Phys. 96(2) 1197 (2004).