EAGER: Multifunctional devices based on coupled phase transitions in antiferromagnetic semiconductors

该项目的智力价值是展示基于反铁磁(AF)半导体的新型多功能器件开发的关键技术。建议的器件将在单个器件中结合非易失性磁存储器和电子晶体管功能，从而解决逻辑电路和存储器实现之间的电流二分法。对于操作设备，将利用相变，与超PS本征磁化动力学相结合，将在两个功能域提供THz速度。如果实现栅感耦合相变，这些器件还将具有改善基本晶体管开关特性的潜力。最后，这些磁性器件将没有边缘磁场，从而实现高密度封装。所提出的器件是金属氧化物-AF-半导体场效应晶体管，MOS(AF)FET，其中移动载流子通过静电选通感应到AF半导体中。这一功能将首次实现对共线AF材料中磁化轴的电检测。在高载流子浓度下，我们预计会发生一系列的金属-绝缘体、反铁磁-铁磁(AF-FM)和结构相变，这将允许静电控制AF主体的电和磁性质。对快速记忆记录特别感兴趣的是通过AF-FM相变在多轴共线AF中旋转磁化轴的可能性，其中磁矩将由几个特斯拉本征交换场产生。对于原型演示，我们将重点介绍NIO。NiO是一种与技术相关的室温共线AF半导体，可以在容易获得的MgO衬底上外延生长。该方案的重点是制备和表征NiO_2基MOS(AF)FET，并演示对AF磁化轴的电检测。该项目的更广泛影响将是开发研究静电诱导的AF-FM相变的使能技术，研究耦合相变的基本物理，以及分析AF半导体中的磁化动力学。参与该项目的学生将参与真正的跨学科研究，架起材料科学、半导体物理和磁学领域的桥梁。国际和平研究所正在开发一门关于磁性半导体物理学的新研究生课程，该课程将利用普渡大学由NSF赞助的NanHUB.org设施向更广泛的受众传播。

Intellectual Merit of the project is to demonstrate key technology toward development of novel multifunctional devices based on antiferromagnetic (AF) semiconductors. The proposed devices will combine non-volatile magnetic memory with electronic transistor functionality in a single device, thus resolving current dichotomy between logic circuitry and memory implementations. For operation devices will utilize phase transitions which, combined with sup-ps intrinsic magnetization dynamics, will offer THz speeds in both functionality domains. The devices will also have a potential to improve on basic transistor switching characteristics if gate-induced coupled phase transitions are realized. Finally, these magnetic devices will have no fringing fields, thus allowing high density packaging. The proposed devices are metal-oxide-AF-semiconductor field-effect transistors, MOS(AF)FET, where mobile carriers are induced into an AF semiconductor by electrostatic gating. This functionality will enable electrical detection of the magnetization axis in collinear AF materials for the first time. At high carrier concentrations we expect a succession of metal-insulator, antiferromagneticferromagnetic (AF-FM) and structural phase transitions, which will allow electrostatic control of both electrical and magnetic properties of the AF host. Of a special interest for fast memory recording is a possibility to rotate the magnetization axis in multi-axis collinear AF by means of AF-FM phase transition, where magnetic torque will be generated by a few tesla intrinsic exchange fields. For prototype demonstrations we will focus on NiO. NiO is a technologically relevant room temperature collinear AF semiconductor which can be epitaxially grown on readily available MgO substrates. The focus of EAGER proposal is to fabricate and characterize NiO?based MOS(AF)FET and to demonstrate electrical detection of AF magnetization axis. The broader impact of this project will be development of the enabling technology for the investigation of electrostatically-induced AF-FM phase transition, study of fundamental physics of coupled phase transitions, and analysis of magnetization dynamics in AF semiconductors. A student working on the project will be involved in a truly interdisciplinary research, bridging fields of material science, semiconductor physics and magnetism. The PI is developing a new graduate course on physics of magnetic semiconductors which will be disseminated to a wider audience using NSF-sponsored nanoHUB.org facility at Purdue University.