Steady-State and Dynamical Measurements of Spin-Dependent Tunneling via Discrete Quantum States

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Non-technical:All electrons carry with them an intrinsic spin, as well as electrical charge. It is therefore possible to control the flow of electrons by acting on their spin (a strategy known as "spintronics") rather than by using conventional techniques which manipulate their charge. This project will investigate the fundamental mechanisms which affect the dynamics of electron spins in nanometer-scale structures and which cause the motion of electrons within these structures to depend on their spin orientation. The research to be pursued will involve comparing the properties of non-magnetic quantum states, few-spin states, and fully-magnetic high-spin states, and how spins can be excited, precess, and relax in these different materials. The work will contribute to the rapid progress now underway to develop and optimize practical spin-based devices such as magnetic field sensors (now used in disk drives) and non-volatile magnetic random access memories. The graduate and undergraduate students to be trained on the project will gain broad expertise in nanofabrication and characterization techniques, as well as skills in presenting their work verbally and in writing, and will be well-prepared to be future leaders in nanotechnology.Technical:This project will utilize electron-tunneling measure-ments of quantized energy levels in nanometer-scale samples to study spin transport in magnetic devices and the dynamics of spin states. By comparing the properties of non-magnetic quantum states, few-spin states, and fully-magnetic high-spin states, the work will seek to characterize the fundamental mechanisms affecting spin-dependent tunneling, spin accumulation and relaxation, and the emergence of collective magnetic properties as a function of increasing exchange-interaction strength. The project will investigate not only steady-state electrical properties, but will also develop experimental techniques to measure the dynamical properties of individual nanoscale magnets as they undergo precession and switching in response to magnetic fields or current-induced torques. This work will be of practical relevance for optimizing magnetic tunnel-junction devices used as sensors in disk drives and for understanding magnetic excitations produced by spin-transfer torques which under investigation for use in non-volatile magnetic random access memory. The graduate and undergraduate students to be trained on the project will gain broad expertise in nanofabrication and characterization techniques, as well as skills in presenting their work verbally and in writing, and will be well-prepared to be future leaders in nanotechnology.