Tuning the competition between ground states in transition-metal oxides by uniaxial pressure

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A conceptually simple avenue to quantum criticality may be found in systems where a nonthermal tuning parameter generates magnetic moments which then can interact to achieve long-range magnetic order. A most promising tuning parameter in this respect is pressure. The basic idea may be simple, the experiments are not. For the cobaltates, ruthenates, and related transition-metal oxides (TMOs) to be studied, effects of hydrostatic pressure are expected to be rather small, and thus uniaxial pressure, a notoriously difficult tuning parameter, needs to be applied. The main method for applying this parameter will be by growing thin films on substrates with various lattice mismatch, a technique that is well established at the IFP. Combining this with additional, variable pressure applied to the thin films in a Bridgman pressure cell will have the additional benefit that different contributions to pressure and strain effects within the film plane and perpendicular to it can be individually studied and disentangled. Thin-film systems also allow direct optical access to the sample surface and thus application of the full gamut of electron spectroscopies available at the soft x-ray analytics facility WERA at the ANKA synchrotron light source for an in-depth study of their electronic and magnetic structure. The associated in-situ thin-film preparation facilities at WERA make this approach unique.