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

在非热调谐参数产生磁矩的系统中，可以找到一种概念上简单的量子临界途径，这些磁矩可以相互作用以实现远程磁有序。在这方面最有希望的调优参数是压力。基本思想可能很简单，但实验却并非如此。对于要研究的钴酸盐、钌酸盐和相关的过渡金属氧化物（TMOs），静水压力的影响预计相当小，因此需要应用单轴压力这个众所周知的难以调节的参数。应用该参数的主要方法将是在具有各种晶格不匹配的衬底上生长薄膜，这是一种在IFP上得到很好建立的技术。将此与附加的可变压力结合在Bridgman压力电池中的薄膜上，将具有额外的好处，即可以单独研究和解开薄膜平面内和垂直于薄膜平面的压力和应变效应的不同贡献。薄膜系统还允许直接光学进入样品表面，从而应用ANKA同步加速器光源的软x射线分析设施WERA中可用的全色域电子能谱，以深入研究其电子和磁性结构。WERA相关的原位薄膜制备设施使这种方法独一无二。

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.