The objective of the proposed program is to realize electric field control of the magnetic state in novel metal spintronic device structures. The approach exploits new and largely unexplored magnetoelectric effects in ultrathin metallic ferromagnetic films. Experiments focus on materials and heterostructures in which the magnetic behavior is dictated by broken symmetries at the surface or interface. Strong electric fields will be used to induce spin-dependent surface charge layers to influence the surface electronic structure and modulate key magnetic parameters (magnetic anisotropy, magnetization, spin polarization and spin-transport characteristics) at surfaces and interfaces. The program will (1) provide fundamental insight, via a systematic experimental dataset, of the mechanisms enabling electric field manipulation of surface magnetism and spin transport and (2) examine specific model devices in which electric fields can excite and control spin dynamics and large-angle magnetic switching. The work addresses the pressing need for efficient modes of operation in advanced spin-based electronics, and avoids key limitations in existing approaches. If successful, these fundamental studies will enable revolutionary new memory and logic device capabilities, offering enhanced performance and durability with ultralow power consumption requirements. The proposed research provides a platform for and will be tightly integrated with educational development at the undergraduate and graduate student level, as well as through involvement of local high school teachers.
Intellectual Merit: The proposed research addresses key fundamental issues in nanoscale magnetism and spin-electronics. Electrical manipulation of the electron spin degree of freedom is one of the forefront areas of nanoscience research today. This program explores new means to electrically manipulate the magnetic state, and will give key fundamental insights on the roles of interfacial electronic structure in the behavior of ultrathin (down to single atomic layer) magnetic materials. Materials systems are chosen such that key parameters (i.e., band level filling) can be continuously tuned in model systems, together with new heterostructures in which novel and heretofore unobserved electric field effects are anticipated. Geometrically-constrained micro- and nano-structures will be fabricated and characterized experimentally and through extensive micromagnetic simulations in order to understand how controlled modulation of magnetic surface anisotropy can be used to drive magnetization dynamics and magnetic switching of spin configurations such as magnetic vortices and magnetic domain walls.
Broader Impacts: If successful, the proposed fundamental research could have broad technological impacts by bringing about new classes of ?spintronic? devices for ultra low-power, high-performance computation and mass data storage, significantly impacting mobile computing and global energy efficiency. The research will train undergraduate and graduate students in key areas in nanotechnology including advanced thin-film growth and characterization, nanofabrication, and spintronics. The program will support an international collaboration between the early-career PI and colleagues at the Max Planck Institute in Halle, Germany, and will offer international scientific training and experience to the supported graduate student. The program integrates research and education by teaming undergraduates with graduate students through the MIT Undergraduate Research Opportunities Program, and through development of course materials and instructional laboratory modules. The PI will make use of the outreach infrastructure of MIT?s Center for Material Science and Engineering (CMSE), and NSF MRSEC, to host high school teachers through the NSF-RET program, and local underrepresented community college students through the CMSE community college program.