Spin Transport and Dynamics in Ferromagnet-Semiconductor Structures

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TechnicalThis project will address the fundamental physics of spin transport and dynamics in hybrid ferrromagnet-semiconductor heterostructures. Devices in which large non-equilibrium spin populations are generated by spin injection will be fabricated, and the effects of spin polarization gradients on both charge and spin transport will be investigated. Mechanisms for spin transport will be probed by exploiting new spin-sensitive electrical detection techniques. Of particular interest are spin-orbit and hyperfine effects, which provide both new means for controlling electron spins as well as potential sources of spin relaxation. The project consists of three components. First, new devices will be developed allowing for the generation of polarization gradients on sub-micron length scales. Second, electrical measurements sensitive to spin dynamics will be used to investigate the coupling of spin and charge transport near the metal-insulator transition in GaAs and InxGa1-xAs. Finally, dynamic coupling between spins in the semiconductor and the ferromagnet will be investigated on nanosecond time scales.Non-technicalMagnetic materials such as iron, cobalt or nickel represent a cornerstone of data storage technologies, and they are also a critical component in sensors for a wide range of applications from cars to cardiac defibrillators. This project will explore the fundamental science of a new class of systems in which magnetic materials such as iron are combined with semiconductors. Graduate and undergraduate students will be trained in the nanofabrication and measurement techniques required to fabricate and study devices based on these materials. Recent research has shown that electrons can be transferred from ferromagnetic metals into semiconductors while preserving magnetic information in the form of their spin, which is analogous to a small magnet attached to the electron. This project will determine how magnetic information can be transported inside semiconductors and then read out electronically. New electronic devices combining very small magnets with thin layers of semiconductor will be developed. New frontiers in the development of extremely small (less than one micron) and fast (less than one billionth of a second) devices will be addressed. The output of this research will be useful in applications where storage and processing capabilities need to be combined in a single circuit element.