NIRT: Building Nanospintronic and Nanomagnetic Structures: Growth, Manipulation, and Characterization at the Atomic Scale DMR Arthur R. Smith, Saw-Wai Hla, Nancy Sandler, and Sergio Ulloa, Ohio University, Athens, OH Nanoscale magnetism is explored by spin-polarized Scanning Tunneling Microscopy (SP-STM) on the Mn 3 N 2 (010) surface using a combination of experiment and first-principles theory. In the left column below, spin- polarized STM data obtained at different positive energies is com- pared with theory performed by NIRT collaborators A. Dick and J. Neugebauer at the Max-Planck- Institut für Eisenforschung GmbH. Energy-dependence of the contrast was found to agree perfectly between experiment and theory, as seen at upper right in a plot of spin contrast versus energy. The excellent agreement shows that spin- polarized STM is THE ideal method for obtaining spin-contrast on surfaces with nanometer-scale resolution, and also confirms the use of the Tersoff-Hammann approach for spin-polarized STM. At right is a plot of the spin-density on the atoms obtained in a section view through the surface. Bright means spin density up; dark means spin density down. Above plot shows optimal agreement between spin-pol- arized contrast from theory and experiment. This interna- tional collaboration was enabled through the NIRT grant support. experimenttheory tip sample surface spin contrast

NIRT: Building Nanospintronic and Nanomagnetic Structures: Growth, Manipulation, and Characterization at the Atomic Scale DMR Arthur R. Smith, Saw-Wai Hla, Nancy Sandler, and Sergio Ulloa, Ohio University, Athens, OH Nanoscale metallic electrodes (in yellow) can be used to confine electrons in small regions, forming quantum dots. Two quantum dots connected to each other form a double quantum dot. In this case, one of the dots is in the Kondo state, in which the magnetic moment of the confined electron (large red arrow) is compensated (“screened”) by the magnetic moment of surrounding electrons, resulting in a zero net magnetic moment for the entire system. L.G.G.V. Dias da Silva et al. Phys. Rev. Lett. 97, (2006) “Dangling Atom” Kondo effect T K. Top panel shows the signature peak of the Kondo effect. Increasing the inter-dot coupling splits the Kondo peak at the Fermi level while increasing the Kondo temperature T K. (Results obtained with NRG methods)

NIRT: Building Nanospintronic and Nanomagnetic Structures: Growth, Manipulation, and Characterization at the Atomic Scale DMR Arthur R. Smith, Saw-Wai Hla, Nancy Sandler, and Sergio Ulloa, Ohio University, Athens, OH Professors Arthur R. Smith (PI-left) and Sergio Ulloa (co-PI-right) prepare to make a team presentation about nanoscience to Southeastern Ohio High School science students within the “Frontiers of Science” lecture series. Ulloa’s portion focused on general ideas of nanoscale science and tech- nology, while Smith focused on the atomic scale, including atoms imaged using STM. The team nano presentation took place at Athens High School in Athens, OH, home of Ohio University. Attendance and stu- dent participation were both high, with ~ 200 students in the high school auditorium observing. The picture at right shows the high school students looking on, as Smith shows a movie (courtesy of NIRT co-PI Saw-Wai Hla) of the atom-by-atom con- struction of the worlds smallest “OU” using silver atoms.