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

非技术摘要：在相关的电子材料中，一种被称为相不均匀的现象被认为是解释这些材料的许多有趣特性的关键。这项工作将探索被称为锰氧化物的相关电子材料中表现出的两种物理现象：与磁有序和巨磁电阻相关的金属-绝缘体转变。本项目将使用富Eu的二元化合物EuO作为研究金属-绝缘体转变和巨磁电阻的简化系统。该项目将全面描述EuO系统中金属-绝缘体的转变，以及寻找富Eu EuO中相不均匀的证据。探索富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理的理解。从长远来看，了解引起有趣现象的电子、磁和结构相互作用的性质，如金属-绝缘体转变或巨磁电阻，可能会为如何将这些材料用于传感器或电子设备等应用提供见解。此外，这项工作将通过对本科生进行实验技术培训，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：相不均匀已成为描述各种相关电子材料的重要范例，包括巨大的磁阻锰氧化物。像锰氧化物一样，富Eu的EuO在低温下表现出巨大的磁阻和铁磁有序，并伴随着绝缘体-金属的转变。然而，与锰氧化物相比，富Eu的EuO为探索金属-绝缘体转变和巨磁电阻提供了一个简化的实验室，因为它的结构复杂性降低了。这一单一研究人员奖将支持对富Eu EuO薄膜的实验研究，目的是根据理论近藤晶格模型描述EuO系统的金属-绝缘体转变和巨磁电阻，以表征输运和磁输运特性。为了探索金属-绝缘体的转变，富Eu EuO薄膜的电阻率将通过控制样品的缺氧量和通过电场效应控制载流子浓度来进行调制。此外，支持的工作将寻找富Eu EuO薄膜磁化和输运行为中相不均匀的间接特征，从而进一步深入了解相不均匀在决定材料性能中的作用。该项目还将对本科生进行实验技术方面的培训，包括样品生长、传输和磁化测量，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.