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

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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.