Phase Transitions in Magnetite and Nickel Sulphide-Selenide Systems

这项研究集中在两个项目上。 第一部分涉及 继续研究磁铁矿和锌铁氧体。 主旨 这项研究的目的是调查镍 硫化物-硒化物系统。 这种材料表现出一种 良好绝缘体、良好金属或金属-绝缘体，x值为 0、2和0.5。 这一特性大概是由 电子相关效应 系统可以通过以下方式进行研究： 改变硫化物/硒化物比率，同时保留阳离子 亚晶格完整 计划开展以下研究： 单晶，然后调整化学计量， 电气测量、磁化研究、特定 热研究、结构研究和光学测量。 的 数据采集不仅是一种内在的兴趣， 用于识别从绝缘状态到 窄带关联态到金属绝缘跃迁 制度，并进入良好的金属行为，在此期间， 晶格基本上保持不变。 因此，数据可以作为 测试电子传输的各种现行理论 政权。

This research is focussed on two projects. The first part involves continued studies on magnetites and zinc-ferrites. The main thrust of this research is directed to the investigation of nickel sulphide-selenide systems. This material exhibits properties of a good insulator, a good metal, or a metal-insulator for x values of 0, 2, and 0.5, respectively. This property presumably is driven by electron correlation effects. The systems can be studied by varying the sulphide/selenide ratio while leaving the cation sublattice intact. The following studies are planned: growth of single crystals, followed by adjustments of stoichiometry, electrical measurements, magnetization investigations, specific heat studies, structural research, and optical measurements. The data acquisition is not just of intrinsic interest but is to be used to identify the changeover from the insulating state, through a narrow band correlated state, to the metal-insulated transition regime, and into the region of good metallic behavior, during which the lattice remains basically unaltered. The data thus serve as a test for current theories of electron transport in the various regimes.