P7: Tuning the competition between ground states in transition-metal oxides by uniaxial pressure

H. v. Löhneysen, S. Schuppler, D. Fuchs, K. Grube

A conceptually simple avenue to quantum criticality may be found in systems where a non-thermal tuning parameter "generates" magnetic moments which then can interact to achieve long-range magnetic order. Among perovskite-derived transition-metal oxides (TMOs), the competition between low-spin and high-spin ground states in certain cobaltates may serve as an example: While for bulk LaCoO3, the Co3+ ions are in the non-magnetic low-spin state at low temperature, LaCoO3 thin films grown with biaxial, tensile strain order ferromagnetically below 85 K. Other TMO systems such as Ca2-xSrxRuO4 show indications for magnetic quantum-phase transitions as well and in conjunction with metal-insulator and/or metamagnetic transitions. We plan to tune the competition between ground states in such systems by applying uniaxial pressure. As a first step, various ways and means for realizing this experimentally will be explored. Electron spectroscopies at IFP’s soft x-ray analytics facility WERA at the ANKA synchrotron will give specific information on the electronic and magnetic structure of strain-tuned TMOs.