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Putting the Electron’s Spin to Work

By Daniel Ralph

Cornell University

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I will discuss recent progress in experimental techniques to control the orientations of nanoscale magnetic moments and electron spins, and to use these new means of control for applications. One powerful new capability arises from the fact that thin magnetic layers can act as filters for spins. During this filtering, spin-polarized currents can transfer some of their spin angular momentum to the magnetic layer, thereby applying a strong torque to the layer. The “spin-transfer torque” provides a very efficient means for manipulating the orientation of small magnets, capable of replacing magnetic fields in many applications. I will discuss progress toward making practical magnetic memory devices and studies of interesting types of spin-torque-driven dynamical states in nanomagnets that are difficult to excite using magnetic fields alone. I will also discuss experiments in which we are working toward extending the control of spins from the 100-nm-scale ferromagnetic devices described above down to individual electron spins in carbon nanotubes and single molecules. We observe signatures of strong spin-orbit coupling in both carbon nanotubes and selected molecules, which may provide an additional all-electrical means of spin manipulation.


Daniel C. Ralph B.S., 1986, Physics and Mathematics, Vanderbilt University. Ph.D., 1993, Physics, Cornell University. Postdoctoral Research Associate, Harvard University, 1993-96. Assistant Professor, Physics, Cornell University, 1996-2000. Associate Professor, Physics, Cornell University, 2000-2004, Professor, Physics, Cornell University, 2004-present. Lester B. Knight Director, Cornell NanoScale Science & Technology Facility (CNF) 2010-present. Alfred P. Sloan Fellow, 1996-99; David and Lucile Packard Foundation Fellow, 1997-2002; William L. McMillan Award, 1997; Research Corporation Research Innovation Award, 1997; ONR Young Investigators Award, 1997-2000.

Research Areas New nanofabrication techniques; electronic properties on molecular length scales; spin transport and high-speed dynamics in magnetic devices; correlated-electron states in magnets and superconductors; quantum properties of defects and impurities.

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  • Daniel Ralph (2011), "Putting the Electron’s Spin to Work,"

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Physics 203, Purdue University, West Lafayette, IN

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