Photoinduced magnetism in

RbjCok[Fe(CN)6]l.nH2O

DiamagneticFeII-CN-CoIII

FerrimagneticFeIII-CN-CoII

Electron transfer andspin crossover

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DiamagneticFeII-CN-CoIII

FerrimagneticFeIII-CN-CoII

Electron transfer andspin crossover

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K3[Fe(CN)6] Co2+

Layer-by-layer deposition from solution

glass or plastic

K3[Fe(CN)6] Co2+

Layer-by-layer deposition from solution

glass or plastic10-100 nm

metal cyanide film

New “assembly at interfaces” method uses benchtop chemistry to produce nanoscale films. Although the compound is cubic, the process generates anisotropic films with properties not known in the bulk.

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The magnetism of a nanoscale film of a molecule-based magnet is controlled by both light and orientation.

A new “optomagnetic” phenomenon for information storage.

Fabrication and Magnetism of Coordinate Covalent Networks Assembled at Interfaces

Daniel R. Talham, University of Florida, DMR-0543362

Franz Frye, Young-Duk Huh, Sarah Lane, and Daniel R. Talham, Department of Chemistry Ju-Hyun Park, Erik Čižmár, and Prof. Mark W. Meisel, Department of Physics

NSF DMR-0305371 (MWM) and NSF DMR-0113714 (MWM and DRT, SQUID Magnetometer)

RbjCok[Fe(CN)6]l.nH2O

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Fabrication and Magnetism of Coordinate Covalent Networks Assembled at Interfaces

Daniel R. Talham, University of Florida, DMR-0543362

A nanoscale thin film of a Prussian blue analog, RbjCok[Fe(CN)6]l.nH2O, shows light-induced changes in magnetization (M) that depend on the orientation of the film. If the magnetic field is parallel to the film, M increases; if perpendicular, M decreases. The property of photoinduced magnetism in this compound was known previously, first published by Hashimoto and colleagues in the late 1990’s, but the anisotropic response in magnetic field is a new discovery.

The photoinduced magnetization is currently a low-temperature phenomenon, and the data shown were obtained at 5 K.

The discovery was made possible because of the thin film fabrication method developed as part of this project. Bulk samples of Prussian blue analogs are poorly crystalline powders and single crystals of the cobalt/iron compound have never been produced. On the other hand, our assembly at interfaces methods often generates oriented thin films, so that single-crystal-like phenomena can be observed. In addition, the interface induces anisotropy into what is otherwise an isotropic cubic structure.

The new magnetic behavior is characteristic of a three-state (or tristable) material, offering the potential of significantly enhanced information density over a binary (or bistable) medium. Also, the optically written information is long-lived and can be switched either thermally or by rotating the magnetic field.

The result was published this year in Applied Physics Letters 85 (2005) 3797-3799. The project is a collaborative one between our group and that of Prof. Mark. W. Meisel in the Department of Physics at UF. Magnetization measurements were obtained with a SQUID magnetometer purchased through an NSF instrumentation grant.

Fabrication and Magnetism of Coordinate Covalent Networks Assembled at Interfaces

Daniel R. Talham, University of Florida, DMR-0543362

Education: This work was conducted as a close collaboration between physics and chemistry groups that are dedicated to the training of young researchers. Three graduate students (Franz Frye, Sarah Lane and physics student Ju-Hyun Park) and two international scholars (Prof. Y.-D. Huh, South Korea, and Dr. E. Čižmár, Slovakia) played key roles in the research. The young researchers receive interdisciplinary training that includes a SQUID magnetometer made possible by NSF DMR-0113714. A biweekly joint physics/chemistry group meeting is shown at right.

Education: Modeling software was purchased with this grant to help elucidate the structure of monolayer networks assembled at interfaces and to help design new targets. The software is also used in the P.I.’s undergraduate inorganic chemistry class to teach students about solid-state chemistry. A snapshop of a 10 picosecond simulation illustrating the role of solvent entropy in precipitation and crystallization is shown at left.