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>> Ferromagnetic Nanostructures with Strong Perpendicular Anisotropy

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Ordered arrays of magnetic mesoscopic elements , whose size ranges from 100 nm to 2 μm [1], are of great significance in understanding nanoscale magnetic phenomena,since they allow the probing of both the individual and collective behavior of the elements in a well controlled and reproducible fashion. It is also of importance to the magnetic recording industry.  The subject is of intense interest for a large number of academic and industrial laboratories around the world.

Fig. 1. AFM image of an FePt dot.  

The basis for the project is the recent discovery [2] in our group of high-symmetry stable magnetic states in disc-shaped nanoparticles with perpendicular anisotropy.  The importance of these findings is that, in contrast to the complex behavior which usually occurs in small elements, these domain structures are highly symmetrical and simple and can thus be studied in detail and manipulated easily.  Magnetic states in particles where a strong symmetry-breaking perpendicular anisotropy interaction is present, are very different than those in low anisotropy materials.  Knowledge of the statics and dynamics of these states is fundamental for the understanding of experiments which are under way in our laboratory.  Motivated by current and upcoming experiments [3,4,5] we concentrate on disc-shaped ferromagnetic particles with uniaxial perpendicular anisotropy.

Fig. 2. Bubble domain in strong perpendicular anisotropy nanodot.  

This project aims to take advantage of the opportunity to combine experiment and theory to test experimentally the existence of the predicted magnetic configurations and to further explore new states and dynamical processes in this system.

The project specifically relies on a collaboration between the Thin Film Magnetism Group and the Theory of Condensed Matter Group at the Cavendish Laboratory   and Tohoku University, Japan (Dr. Toshiyuki Shima).

Selected references:

[1] M. Kldui, C.A.F. Vaz, L. Lopez-Diaz and J.A.C. Bland, J. Phys.:Condens. Matter15, R985 (2003)
[2] S. Komineas, C.A.F. Vaz, J.A.C. Bland and N. Papanicolaou,Phys. Rev. B71, 060405(R) (2005)
[2] L.D. Buda, I.L. Prejbeanu, M. Demand, U. Ebels and K. Ounadjela,I.E.E.E. Trans. Magn.37, No 4 (2001)
[4] P. Eames and E. Dan Dahlberg, J. Appl. Phys.91, 7986 (2002); G.D.Skidmore et al., Phys. Rev. B70, 012410 (2004)
[5] T. Shima, K. Takanashi, Y.K. Takahashi, K. Hono, G.Q. Li and S.Ischio, J. Magn. Magn. Mater.266, 171 (2003)

Link to Thin Film Magnetism group Research Projects : Research projects