Acquisition of SQUID Magnetometer - Susceptometer with Resistivity and Hall Effect Measurement Option

9318333 Schweitzer具有交流磁化率、电阻率和霍尔效应测量能力的SQUID磁强计将用于研究层状硫化物合金的电输运和磁性。该研究项目将研究我们最近在BaCo1-xNixS2-y系统中发现的不寻常的金属-绝缘体转变。这一一级相变是从半导体相向金属相的转变，随温度降低。低温相是高度相关的金属，而高温相似乎是二维反铁磁体。相变温度和磁滞与化学成分有关。与转变相关的热双稳和正的电阻率温度系数表明，这些材料在材料研究和工程中有许多实际应用。转变时的大电阻变化，通过改变组成来控制性能的能力，以及材料的稳定性，都有利于应用。该实验计划还将涉及可能出现类似现象或可能具有超导电性的相关三元硫化物和硒的合金的探索性合成和表征。所需设备将用于测量所发现的所有相的直流磁化、交流磁化率、电阻率和霍尔系数。在某些层状三元硫化物中存在这种不寻常的相变是对以前未知现象的重大发现。对这些材料的研究有助于我们理解高度相关的电子系统、金属-绝缘体的转变，甚至高温超导。***

9318333 Schweitzer The SQUID magnetometer with AC susceptibility, resistivity, and Hall effect measurement capabilities will be used to study the electrical transport and magnetic properties of layered sulfide alloys. The research project will investigate the unusual metal- insulator transition thansition that we have recently discovered in the BaCo1-xNixS2-y system. This first-order phase transition is from a semiconducting to a metallic phase with decreasing temperature. The low temperature phase is a highly correlated metal, while the high temperature phase appears to be a two- dimensional antiferromagnet. The transition temperature and hysteresis depend on the chemical composition. The thermal bistability and positive temperature coefficient of resistivity associated with the transition suggest that these materials could be useful for many practical applications in materials research and engineering. The large resistance change at the transition, the ability to control the properties by varying the composition, and the stability of the materials are all favorable for applications. %%% The experimental program will also involve exploratory synthesis and characterization of related ternary sulfide and selenide alloys that might exhibit similar phenomena or possibly superconductivity. The equipment requested will be used to measure the DC magnetization, AC magnetic susceptibility, resistivity, and Hall coefficient of all phases found. The existence of this unusual phase transition in certain layered ternary sulfides is a significant discovery of previously unknown phenomena. Study of these materials can contribute to our understanding of highly correlated electronic systems, metal- insulator transitions, and perhaps high temperature superconductivity. ***