Magnetic phase transitions in two-dimensional films

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Even though everything has three spatial dimensions, in some cases the third dimension is so small that an object acts precisely as if it is two-dimensional. An example of this is the magnetic behaviour of an ultrathin film. A film of magnetic atoms, such as iron or nickel, that is only one atom thick can be deposited on a substrate that is non-magnetic. The magnetic behaviour of the film is profoundly affected by its two-dimensionality, especially with regard to the possible stable magnetic states, their orientation, and range of stability as the temperature is changed. This proposal aims to study magnetism in two-dimensional ultrathin magnetic films grown in ultrahigh vacuum and probed by magneto-optical interactions between the film magnetism and laser light. Specific projects involve fabricating and studying phase transitions in ferromagnetic films with no preferred direction of magnetization, with patterns of magnetic domains, and in antiferromagnetic films.