Grant: Discovery Grants Program - Individual

Advances in permanent magnetism, magnetic recording and high-frequency materials are behind much of the progress which has been made in motor and transformer technology, computers and telecommunications over the course of the twentieth and twenty-first centuries. The properties are determined by the ground state, or the most energetically favourable magnetic structure or spin configuration within the material. The lifetime of the system when excited to a higher energy state also has important consequences. In practical devices, magnetic excitations constrain the characteristic timescales and lengthscales over which a nonequilibrium spin population may be controlled, which underpins data storage and manipulation. In model magnetic systems, an understanding of the excitations sheds light on the underlying spin interactions. My focus is the experimental investigation of magnetic fluctuations and magnetisation dynamics using mainly magnetic resonance spectroscopy techniques in concert with magnetisation, magnetotransport and neutron scattering. Four arenas are proposed, ranging from artificial heterostructures of relevance for spin transport applications to model geometrically frustrated magnetic materials, where it is not possible to satisfy all the magnetic interactions simultaneously, leading to "finely balanced" systems with many equally favourable, potentially novel ground states. Such geometric magnetic frustration is ubiquitous within condensed matter physics. The underlying goal is a greater understanding of how the magnetic structure and excitations of the systems evolve as a function of tuning parameters like temperature, pressure, applied magnetic field or chemical composition. This is particularly important in the neighbourhood of phase transitions between magnetic ground states. In addition, through the application of microwaves or electric currents, we aim to manipulate the spin populations and seek evidence of that manipulation by characterising the spatial and temporal variation in the internal magnetic fields within the system of interest. It is anticipated this collaborative program of research will yield insight, at a microscopic level, into the role of constraints or boundary conditions, like interfaces in thin film interfaces, in governing their magnetic properties. It will provide an opportunity to train people in the fundamentals of magnetic interactions in transition metal and rare earth based compounds using a combination of complementary bulk and spectroscopic techniques. It will also contribute to the understanding and hence future development of improved artificial heterostructures for data manipulation and storage.