Our research activities have been focused on the modeling of structural, magnetic and dynamical properties of nanostructured magnetic materials through the application of numerical techniques including Monte Carlo simulations and electronic structure calculations.

 

Current research topics include

  • Nanoparticle systems and films
  • Magnetic semiconductors at the nanoscale
  • Perovskites for energy harvesting
 

Magnetic behaviour of nanoparticle systems for biomedical , magnetic recording and energy applications

The properties of magnetic nanoparticles are dramatically different from those of the bulk materials. They are modified by the presence of the nanoparticle surface, of defects and of a different magnetic phase. The aim of our work is to reveal the various factors that control the magnetic behavior of nanoparticles and suggest optimum parameters for magnetic recording and magnetic hyperthermia applications and energy applications.

      

Assemblies of magnetic nanoparticles (NPs) are met most often in naturally occurring systems and in man-made structures such as granular solids, patterned structures, self-organized arrays. Interparticle interactions have inevitable effects on the global magnetic behavior of a sample and introduce a rich structure to the phase diagram of the assembly as the packing density increases. The magnetic domain structure is rather complex due to competition between the short range exchange forces acting between nanoparticles "in-contact" and the long range dipolar interactions.

      Magnetic Ferrofluids

  When magnetic nanoparticles are allowed to move in a carrier, driven by thermal agitation (Brownian motion) and their mutual interactions (magnetostatic), they tend to form well defined shapes such as chains and loops, or more complicated structures such as branching points and labyrinths, whose statistical morphology can be characterized as a fractal. The potential of systems with a non-magnetic liquid carrier, known as ferrofluids, in medical applications (drug delivery) and technological applications (magnetic field sensors) brings these systems at the frontiers of current scientific interest. The aggregation mechanism and the resulting fractal morphology depend on internal parameters (particle size distribution, magnetic moments, particle shape, interparticle interactions, particle-carrier interactions, particle density) and external conditions (temperature, applied field). Physical properties such as magnetization, moment-moment correlation function and magneto-optical properties (refraction index) are characterized by scaling exponents that are strongly dependent on the growth conditions of the aggregate.

    Diluted magnetic Semiconductor Nanostructures

We investigate the microscopic mechanism of ferromagnetism in II-VI and III-V semiconductor nanostructures containing a random distribution of magnetic ions, usually Mn. In our study we combine Monte Carlo simulations of the magnetic structure with total energy calculations performed by an exact diagonalization of the Hamiltonian for the coupled carrier-local moments system.

    Perovskites for energy harvesting In the area of photovoltaic materials, we are looking at novel compounds, like perovskites of the form Cs2SnXxY6-x, X, Y=Cl, Br, I, which are promising in terms of both stability and efficiency. Density Functional Theory techniques are employed, in order to predict properties of interest (band gap and band structure, transport properties etc.).


Research Collaborator

Dr. George Margaris

Recent Books/Chapters

  •  Vasilakaki, G. Margaris, E. Eftaxias, and K. N. Trohidou (2017), Monte Carlo Study of the Exchange Bias Effects in Magnetic Nanoparticles with Core–Shell Morphology  In Exchange Bias: From Thin Film to Nanogranular and Bulk Systems, (ed. Surender Kumar Sharma)  Taylor & Francis Books, ISBN 9781498797238 Ch. 6 [link]

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  • Magnetic Nanoparticle Assemblies Kalliopi Trohidou (Editor), 306 pages, Pan Stanford Publishing (Publisher) 2014 Print ISBN: 9789814411967 eBook ISBN: 9789814411974 DOI: 10.4032/9789814411974M.

  • Vasilakaki, G. Margaris and K. Trohidou, (2014) Magnetic Behavior of Composite Nanoparticle Assemblies, Magnetic Nanoparticle Assemblies (ed. K. N. Trohidou) Pan Stanford Publishing 251-284. [link]

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  • M. Vasilakaki, G. Margaris and K. Trohidou (2012) Monte Carlo simulations on the magnetic behaviour of nanoparticle assemblies: Interparticle interactions effects, Nanoparticles Featuring Electromagnetic Properties: From Science to Engineering (ed. Alessandro Chiolerio and Paolo Allia) Signpost, Kerala, India 105-132. [link]

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  • K. Trohidou and M. Vasilakaki (2011)Monte Carlo Studies of Magnetic Nanoparticles, Applications of Monte Carlo Method in Science and Engineering (ed. S. Mark and S.Mordechai) InTech, Croatia 513-538. [link]

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  • K. N. Trohidou (2005) Monte Carlo Studies of Surface and Interface Effects in magnetic Nanoparticles, Surface Effects in Magnetic Nanoparticles (ed. D. Fiorani) Springer Science, USA 45-70. [link]

Running Grants

 

 

 

Horizon 2020- FET Proactive – Boosting emerging technologies: Title “MAGnetic nanoparticle based liquid ENergy materials for Thermoelectric device Applications”
Contract No 731976
Duration: 1/01/2017-31/12/2020
https://www.magenta-h2020.eu


 

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ARISTEIA 1 “Complex Magnetic nanostructures” Period: 28/09/2012-31/12/2015 Excellence Grant from the Greek Government and EU

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