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

我们申请了一个测量站“应变”，由高场氦低温恒温器，测量单元和电子设备组成。该空间站将能够在宽低温环境（1.8K-约400 K）和高达17 T的高磁场中对各种材料进行测量-这是一种决定性的环境，可以获得量子材料的独特性能。应变是一个编码材料的各种有趣和独特性质的物理量。通过在先进的样品环境中测定这些量，我们将对量子材料领域的不同项目做出决定性的贡献，我们将研究大的单轴应变对Co基反铁磁体（Sr 1-xCax）Co2 As 2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.外部对称性破缺甚至可以诱导新的相位，否则是不稳定的。此外，应变可能会导致临界行为，因此可以作为一个独特的“调谐参数”。热应变的精确测定（即，热膨胀系数）和磁致伸缩系数的研究，并进一步研究了Fe（Se，S）在其双量子临界点附近的应变行为（热膨胀系数、磁致伸缩系数、弹性模量、外加单轴应变的影响）。虽然向列有序与各向异性应变有着内在的联系，但人们对Fe（Se，S）在低温和强磁场下的应变行为知之甚少。此外，我们还将研究范德瓦耳斯铁磁体FeNGeTe_2（N= 3，4，5）和超导绝缘体KFe_（0.8）Ag_（1.2）X_2（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)].