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，一种被称为相位不均匀性的现象被认为是解释这些材料许多有趣性质的关键。这项工作将探索两个物理现象，已被展示在相关的电子材料称为锰氧化物：与磁有序和巨磁阻相关的金属-绝缘体转变。本计画将以富铕二元化合物EuO作为研究金属-绝缘体转变与巨磁电阻的简化系统。该项目将全面表征EuO系统中的金属-绝缘体转变，并寻找富Eu EuO中相不均匀性的证据。探索富铕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。从长远来看，了解电子，磁性和结构相互作用的性质，这些相互作用会引起有趣的现象，如金属-绝缘体转变或巨磁阻，可以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，这项工作将有助于通过培训本科生的实验技术，包括样品生长和物理特性测量，满足对技术劳动力日益增长的需求。技术摘要：相位不均匀性已经成为描述包括巨磁阻锰氧化物在内的各种相关电子材料的重要范例。像锰氧化物，富铕EuO表现出巨大的磁阻和铁磁有序在低温下伴随着绝缘体-金属的转变。然而，富Eu的EuO提供了一个简化的实验室探索的金属-绝缘体转变和巨大的磁阻，因为它降低了结构的复杂性相比，锰氧化物。 这个单一的研究者奖将支持富铕EuO薄膜的实验研究，其目的是根据理论Kondo晶格模型来描述EuO系统的金属-绝缘体转变和巨磁阻，从而表征传输和磁输运性质。为了探索金属-绝缘体转变，富Eu的EuO薄膜的电阻率将通过控制样品的缺氧和通过电场效应控制载流子密度来调制。此外，所支持的工作将寻找富Eu EuO薄膜的磁化和传输行为中的相不均匀性的间接特征，从而进一步了解相不均匀性在确定材料特性中的作用。 该项目还将在实验技术方面培训本科生，包括样品生长和运输以及磁化测量，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.