Measuring station "strain" in a high-field helium cryostat

我们申请了一个由高场氦低温恒温器、测量单元和电子器件组成的“应变”测量站。空间站将能够在宽阔的低温环境(1.8K-约400K)和高达17T的强磁场中对各种材料进行测量--这一环境对获得量子材料的独特性质具有决定性意义。应变是一个热力学参数，它编码了一种材料的各种有趣和独特的性质。通过在先进的样品环境中测定这些量，我们将在量子材料领域的不同项目中做出决定性的贡献。我们将研究大单轴应变对Co基反铁磁材料(SR1-xCax)Co2As2的影响。这种材料表现出复杂的磁性，预计外部应变将导致不同类型的磁序之间的切换。外部对称性的破缺甚至可能诱导出原本不稳定的新相。此外，压力可能会让人接触到关键行为，从而充当一个独特的“调整参数”。此外，我们还将研究Fe(Se，S)在其向列相量子临界点附近的应变行为(热膨胀系数，磁致伸缩，弹性模量，外部单轴应变的影响)。Fe(Se，S)目前具有仍然神秘的向列相的模型系统的作用。虽然向心仪与各向异性应变有内在联系，但对Se，S在低温和强磁场中的应变行为知之甚少。此外，我们还将研究范德华铁磁体FeNGeTe2(N=3，4，5)和向列相绝缘体KFe0.8Ag1.2X2(X=S，Se，Te)的应变行为。

We apply for a measurement station „strain“ that consists of a high-field Helium-cryostat, measurementcell and electronics. The station will enable measurements on diverse materials in a broad andcryogenic temperature environment (1.8K-ca.400K) and in high magnetic fields up to 17T – an environmentthat is decisive to access the unique properties of quantum materials. Strain is a thermodynamicquantity that encodes a variety of interesting and unique properties of a material. By determiningthese quantities in an advanced sample environment, we will achieve decisive contributionsto different projects in the area of quantum materials.The effect of large uniaxial strain on the Co-based antiferromagnets (Sr1-xCax)Co2As2 will be studied.This material exhibits complex magnetism and it is expected that the external strain will case switchingbetween different types of magnetic order. The external symmetry breaking may even inducenew phases that are otherwise not stable. In addition, strain may give access to critical behavior andthus act as a unique “tuning parameter”. Accurate determination of thermal strain (i.e., thermal expansivity)and magnetostriction will complete the project.Furthermore, we will study the strain behavior (thermal expansivity, magnetostriction, elastic moduli,influence of external uniaxial strain) of Fe(Se,S) in proximity to its nematic quantum critical point.Fe(Se,S) has by now the role of a model system for the still-enigmatic nematic phase. Although nematicorder is intrinsically linked to anisotropic strain, little is known about the strain behavior ofFe(Se,S) at low temperature and in high magnetic fields. Our measurements will thus make an importantcontribution to clarify the behavior of superconductivity arising around a nematic quantumcritical point.In addition, we will study the strain behavior of the family of van-der-Waals ferromagnets FeNGeTe2(N=3,4,5) and of the nematic insulator KFe0.8Ag1.2X2, (X=S,Se,Te)].