RUI: EuO Thin Films as a Laboratory for Exploring Metal-Insulator Transitions and Colossal Magnetoresistance

非技术摘要：在相关电子材料中，一种被称为相不均匀的现象被认为是解释这些材料许多有趣性质的关键。这项工作将探索在被称为锰矿石的相关电子材料中已经展示的两种物理现象：与磁有序和巨磁电阻相关的金属-绝缘体转变。本项目将采用二元富铕化合物EuO作为研究金属-绝缘体跃迁和巨磁阻的简化体系。该项目将全面表征EuO体系中的金属-绝缘体转变，并寻找富含eu的EuO中相不均匀性的证据。探索富含eu的EuO系统与其他相关电子系统的相似性可以增强对这些材料性质的机制的理解。了解电子、磁性和结构相互作用的本质，这些相互作用会产生有趣的现象，如金属-绝缘体过渡或巨大的磁电阻，从长远来看，可能会为如何利用这些材料用于传感器或电子设备等应用提供见解。此外，这项工作将通过培训本科生实验技术，包括样品生长和物理性质测量，帮助满足对技术劳动力日益增长的需求。技术摘要：相不均匀性已经成为描述各种相关电子材料的重要范例，包括巨磁阻锰矿。像锰一样，富铕铕在低温下表现出巨大的磁阻和铁磁有序，并伴有绝缘体-金属转变。然而，富eu - EuO为探索金属-绝缘体过渡和巨大磁阻提供了一个简化的实验室，因为它的结构复杂性比锰矿石低。这个单一研究者奖将支持富铕EuO薄膜的实验研究，目的是根据理论的kondo晶格模型来描述EuO系统的金属-绝缘体转变和巨磁电阻，从而表征输运和磁输运特性。为了探索金属-绝缘体的转变，富铕EuO薄膜的电阻率将通过控制样品的氧缺乏和通过电场效应控制载流子密度来调节。此外，支持的工作将寻找富铕EuO薄膜磁化和输运行为中相不均匀性的间接特征，为相不均匀性在决定材料性能中的作用提供额外的见解。该项目还将培训本科生实验技术，包括样品生长、运输和磁化测量，从而帮助培养未来的物理学家。

Non-technical abstract: In correlated electron materials, a phenomenon known as phase inhomogeneity is thought to be critical for explaining many interesting properties of these materials. This work will explore two physical phenomena that have been exhibited in correlated electron materials known as manganites: a metal-insulator transition associated with magnetic ordering and colossal magnetoresistance. This project will employ the binary compound Eu-rich EuO as a simplified system for studying the metal-insulator transition and colossal magnetoresistance. This project will fully characterize the metal-insulator transition in the EuO system, as well as searching for evidence of phase inhomogeneity in Eu-rich EuO. Exploration of the similarities of the Eu-rich EuO system to other correlated electron systems can enhance understanding of the mechanisms that are responsible for the properties of these materials. Understanding the nature of electronic, magnetic, and structural interactions that give rise to interesting phenomena, like the metal-insulator transition or colossal magnetoresistance, in the long run may provide insights as to how to take advantage of these materials for applications such as sensors or electronic devices. Additionally, this work will help meet the growing demand for a technical workforce by training undergraduates in experimental techniques, including sample growth and physical properties measurements. Technical abstract:Phase inhomogeneity has emerged as a significant paradigm for describing a wide range of correlated electron materials, including the colossal magnetoresistive manganites. Like the manganites, Eu-rich EuO exhibits colossal magnetoresistance and ferromagnetic ordering at low temperatures with an accompanying insulator-metal transition. However, Eu-rich EuO provides a simplified laboratory for exploring the metal-insulator transition and colossal magnetoresistance because of its reduced structural complexity as compared to the manganites. This single investigator award will support an experimental study of Eu-rich EuO thin films with the objective of characterizing the transport and magnetotransport properties in light of the theoretical Kondo-lattice model that has been developed to describe the metal-insulator transition and colossal magnetoresistance of the EuO system. To explore the metal-insulator transition, the resistivity of the Eu-rich EuO films will be modulated both by controlling the oxygen deficiency of the samples and by controlling the carrier density via the electric field effect. Additionally, the supported work will look for indirect signatures of phase inhomogeneity in the magnetization and transport behavior of the Eu-rich EuO thin films, providing additional insight into role of phase inhomogeneity in determining material properties. This project will also train undergraduates in experimental techniques, including sample growth and transport and magnetization measurements, thereby helping to develop future physicists.