Numerical simulations of magnetic systems with competing interactions

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Magnetic phenomena can occur in a huge variety of materials.  With advances in computing power, we are able to learn more about how magnetic moments are arranged in increasingly complex systems.  These moments can be associated with individual atoms in a crystal or as a part of larger nanometer clusters in thin films.  In each case, the geometry of the system plays a major role in determining the arrangement of the magnetic-moment directions, which can be quite complex. Numerical techniques have been developed to study how the orientation of the magnetic moments change with changing temperature, pressure, and applied magnetic field.  The details of the moment orientations on a microscopic level determine how larger samples of the materials will behave in the laboratory and in real device applications.     Part of our work will focus on geometrically frustrated antiferromagnets, where the interactions between neighboring atoms in a crystal cannot all satisfy the preference of the atomic magnetic moments to be anti-parallel. New examples of frustrated antiferromagnetic materials are being discovered regularly, such as those which also exhibit the technologically important magnetoelectric effect where an applied magnetic field induces a detectable voltage. Our numerical techniques will be applied to further understand this exciting and potentially significant new phenomenon.    A related focus of our work is on thin ferromagnetic films of interest to the data storage industry for a variety of purposes.  This includes materials used in hard drives.  As the density of data increases, the magnetic grain size must decrease until the superparamagnetic limit is reached, where thermal motion causes spontaneous moment reversal and data is lost.  Our work will aid in revealing what properties of the thin films are needed to prevent this from occurring.      A significant benefit of the theoretical and numerical studies we perform is the close collaboration with experimental groups at Memorial and elsewhere.  This can be particularly rewarding for trainee researchers.