Magnetic Nanosystems: Making, Measuring, Modeling and Manipulation
Viatcheslav Dobrovitski, Bruce Harmon, Myron Hupalo, David Johnston, Marshall Luban, Ruslan Prozorov, Michael Tringides, David Vaknin, Jerel Zarestky
Kyuil Cho, Wei Tian, Zhihui Wang
This project is designed to meet the challenge of synthesizing and characterizing new magnetic materials whose basic unit is of nanometer size. This Project will expand the coordinated efforts of recent years in the synthesis and characterization of magnetic molecules so as to target a wider array of nanoscale magnetic systems. Strong collaborative ties with scientists at national and international institutions and facilities enhance the Ames effort. In-house experimental facilities probe spin interactions (when necessary down to millikelvin temperatures) by NMR, fast optics, x-ray, susceptibility, and neutron scattering techniques. This project also includes a strong theory component using analytical methods, classical and quantum simulation tools, and first-principles electronic structure methods.
Subtasks in this project are:
- Magnetic molecules. An established centerpiece of this entire Project is the study of single crystals composed of nanometer-size magnetic molecules. In future work we will manipulate the synthesis process so as to systematically track the emergence of cooperative, macroscopic magnetic phenomena in 1, 2, and 3 dimensions for a matrix of nano-size building blocks. We will also expand our study of quasi-one-dimensional (1D) and 2D magnets, where the magnetic entities have a nanoscale dimension in two and one dimensions, respectively. The above systems include magnetic geometries leading to spin frustration, a novel state of matter. (M. Luban, Y. Furukawa, D. Johnston, R. Prozorov, V. Dobrovitski, D. Vaknin, J. Zaretsky, B. Harmon). Formal collaborations exist with Paul Koegerler (Jülich) and Christian Schröder (Bielefeld)
- Single and few spin systems. Investigations of single-spin and few-spin quantum dynamics, in such nanostructures as quantum dots and spin impurity centers in crystals, will help to understand the environmental interactions affecting spin systems and will lead to ways for controlling and suppressing the decoherence of spins in nanostructures. Powerful and accurate numerical techniques, together with modern analytical approaches will be used. Experimentally, fast optical probes will be used to detect and coherently manipulate spin coherence, and assess and control relaxation. Advanced spin resonance techniques will also be employed. (V. Dobrovitski, B. Harmon, Y. Furukawa)
- Magnetic nanostructures on surfaces. This subtask will use a different approach for self-assembly and the creation of nanoscale spin systems. Magnetic species will be deposited on graphene (for optimal mobility and limited chemical activity), and island formation monitored. Magnetic STM tips will be used to probe the magnetism distribution on the island, and fast probe optical Kerr effects will explore the dynamics. Spin polarized first principles electronic structure calculations will be used to investigate the quantum size effect and magnetic response. (M. Tringides, M. Hupalo, C.-Z. Wang)
Fielden J; Ellern A; Kogerler P . 2010. [Cr-8(PhCO2)(16)O-4]center dot 4CH(3)CN center dot 2H(2)O: structural origin of magnetic anisotropy in a molecular spin cluster. Acta Crystallographica Section C-Crystal Structure Communications. 66:253-256.
Schroder C; Fang X; Furukawa Y; Luban M; Prozorov R; Borsa F; Kumagai K . 2010. Spin freezing and slow magnetization dynamics in geometrically frustrated magnetic molecules with exchange disorder. Journal of Physics-Condensed Matter. 22:216007.
Das S; Niazi A; Mudryk Y; Pecharsky V K; Johnston D C . 2010. Magnetic, thermal, and transport properties of the mixed-valent vanadium oxides LuV4O8 and YV4O8. Physical Review B. 81:104432.
Fang X K; Speldrich M; Schilder H; Cao R; O'Halloran K P; Hill C L; Kogerler P . 2010. Switching slow relaxation in a (Mn3MnIV)-Mn-III cluster: an example of grafting single-molecule magnets onto polyoxometalates. Chemical Communications. 46:2760-2765.
Engelhardt L; Luban M . 2010. Simple models and powerful tools for seeking a comprehensive understanding of the magnetic properties of molecular magnets. Dalton Transactions. 39:4687-4692.
Nath R; Furukawa Y; Borsa F; Kaul E E; Baenitz M; Geibel C; Johnston D C . 2009. Single-crystal P-31 NMR studies of the frustrated square-lattice compound Pb-2(VO)(PO4)(2). Physical Review B. 80:214430.
Li T; Hupalo M; Tringides M C; Wang J . 2009. Ultrafast Dynamics of Highly Excited Dirac Fermions in Few-Layer Graphene: Evidence for Three-Particle Auger Scattering. MRS Proceedings. 1230:MM02-06.
Fielden J; Long D L; Cronin L; Kogerler P . 2009. Synthesis of Cu(I) octamolybdates using tetrakis-acetonitrilecopper(I) hexafluorophosphate. Polyhedron. 28:2803-2807.