Magnetic Nanoparticle Assemblies

Project Summary

The aim of the project is to understand and predict the magnetic properties of dense (interacting) assemblies of magnetic nanoparticles by considering the interplay between: (i) intrinsic dynamics, governed mainly by the effective or single-particle anisotropy and the effective exchange coupling  between different magnetic components forming the nanoparticle, such as the core, the shell, the surface, etc and (ii) extrinsic dynamics, governed by interparticle interactions such as exchange and magnetostatic. The effective parameters (magnetic moment, anisotropy energy) describing the intrinsic dynamics of the nanoparticles are obtained either in an empirical way, namely by fitting to experimental measurements or by a multiscale modeling approach from atomic scale parameters (atomic moments, single-ion anisotropy, etc) which are more reliably measured or known from ab initio electronic structure calculations. We model assemblies with various morphologies including random systems, ordered arrays and chain-like structures and calculate experimentally attainable quantities such as isothermal magnetization hysteresis loops and temperature dependent magnetization under various measurement protocols (ZFC/FC, etc) using mainly Monte Carlo algorithms.

Review articles on our work

- A book chapter on the fundamental ideas and models related to the magnetic properties of single-domain magnetic nanoparticles.

- A review article on the magnetic and transport properties of ordered arrays of magnetic nanoparticles.

Selected Publications

D. Kechrakos, K. N. Trohidou and M. Vasilakaki,

Magnetic properties of dense nanoparticle arrays with core/shell morphology,

J. Magn. Magn. Mater. 316 (2): E291-E294 SEP (2007)

D. Kechrakos and K.N. Trohidou,

Magnetic Properties of Self-Assembled Interacting Nanoparticles,

 Appl. Phys. Lett. 81  4574-4576 (2002)

C. Binns, M. J. Maher, Q. A. Pankhurst, D. Kechrakos, and K. N. Trohidou, 

Magnetic behaviour of nanostructured films assembled from preformed Fe clusters embedded in Ag, 

Phys. Rev. B 66 184413, (2002)

D. Kechrakos and K. N. Trohidou, 

Magnetic properties of dipolar interacting single-domain particles, 

Phys.Rev. B 58, 12169-12177 (1998)