****NON-TECHNICAL ABSTRACT**** Continued technological development depends on the advanced understanding of phenomena specific to nanoscale systems, and the ability to harness the phenomena for application in nanodevices. The goal of this Faculty Early Career Development project at West Virginia University is to explore new physical phenomena in nanoscale magnetic devices. Such devices promise higher speed and smaller power consumption compared to the conventional semiconductor devices. The functionality of nanomagnetic devices is associated with changes of their magnetic configuration, which can be efficiently achieved by passing an electrical current through the device. The goal of this project is to establish the scope of current-induced phenomena in nanomagnetic devices. The project will investigate whether using advanced magnetic materials with complex magnetic properties can enhance the efficiency of manipulation of magnetic nanodevices by electrical current. Additionally, new current-induced effects in magnetic devices will be probed, expanding the range of configurations achievable by applying an electrical current. The research goals of the project will be complemented by a comprehensive nanoscience education program, which includes a science camp for middle school students and development of a nanoscale physics course in the framework of the nanoscience minor at WVU.
Future technological development relies on the advanced understanding of phenomena specific to nanoscale systems, and the ability to harness the phenomena for application in nanodevices. Magnetic nanodevices are a promising replacement for the conventional semiconductor devices. Their configuration can be manipulated by spin polarized electrical currents, which can rotate the magnetic moments via the spin transfer torque exerted by polarized electrons. The goal of this Faculty Early Career Development project at West Virginia University is to explore new current-induced phenomena in nanomagnetic devices that can make the manipulation of magnetic devices by current more efficient. The project will address the possibility of expanding the scope of manipulation by spin transfer to complex magnetic systems including antiferromagnets, and to magnetic configurations in which the usual spin torque becomes inefficient. The research goals of the project will be complemented by a comprehensive nanoscience education program, which includes a science camp for middle school students and development of a nanoscale physics course in the framework of the nanoscience minor at WVU.
Traditionally, the properties of magnetic materials have been studied by measuring their response to external magnetic fields. Similarly, magnetic devices such as magnetic sensors commonly found in cars have exploited the effects of magnetic fields. The project has experimentally investigated the possibility to use electron spin currents, applied to magnetic structures instead of magnetic fields, to control the state of nanomagnetic systems and to learn about their properties. The main technical outcome of this investigation was the development of two novel types of spin torque nano-oscillator (STNO) devices – active nanomagnetic devices capable of coherent microwave and spin wave generation. One of the developed devices is based on the spin Hall effect, and another is based on the nonlocal spin injection mechanism as the source of spin current. Studies of these, as well as the more traditional magnetic multilayer-based STNO resulted in a new level of the fundamental understanding of the effects of spin current. Namely, it was shown that the spin current injection into ferromagnets results in the formation of a new localized dynamical state not present in the unperturbed nanomagnetic system. The spatial and spectral characteristics of this state are determined by the nonlinear dynamical and geometric properties of the magnetic system and the geometry spin injection. These findings enabled us to develop completely new types of STNO-based nanodevices, whose characteristics are judiciously controlled by engineering their geometry (see Figure). Scientific merits The project has resulted in a new level of fundamental understanding of the dynamical properties of nanoscale magnetic systems driven far out-of-equilibrium by electric currents. This new understanding is relevant not only to magnetic systems, but to many other nonlinear multimodal dynamical systems, including optically active media (e.g. lasers), excitonic and plasmonic systems. Broader impacts The demonstrated current-induced effects enable new types of magnonic devices –magnetic structures that can utilize spin waves for the storage, transmission and manipulation of information. Such devices can find applications as the integrated on-chip replacements of the traditional charge-based semiconductor devices. In addition to the direct impact of the research findings, the project impacted the society at large by specific education/outreach components that included the development and sustained annual implementation of a week-long summer science camp for middle school students, annual science day and science festival, and development of the educational curriculum for a new materials science/engineering program at Emory University.
