2006 Fiscal Year Final Research Report Summary
Design and characterization of photo-controllable magnetic materials
| Project/Area Number |
14050089
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Review Section |
Science and Engineering
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| Research Institution | Keio University |
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Principal Investigator |
EINAGA Yasuaki Keio University, Department of Chemistry, Associate Professor (00322066)
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| Project Period (FY) |
2002 – 2006
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| Keywords | Magnetic materials / Photo-functional materials / Photo-control / Ferromagnetic / Photochromic compounds / Naoparticles |
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| Research Abstract |
We have reported several examples of novel photo-switching magnetic systems containing photochromic compounds and magnetic materials. That is, the magnetic properties can be controlled by photoisomerization of the photochromic compounds.
In order to realize reversible photo switching of magnetization at room temperature, we have focused on a surface modification of nano-scale magnetic particles and a combination of photochromic azobenzene-containing amphiphilic compounds and the magnetic nanoparticles as magnetic materials that can function at room temperature. The magnetic iron oxide nanoparticles, with an estimated average size of 5nm, were encapsulated with an azobenzene-containing amphiphilic compound. Photoisomerization of the azo moiety (trans/cis) affected the electrostatic field around the magnetic nanoparticles. As a result, we were able to reversibly control the magnetic properties of this composite material by photo-illumination in the solid state at room temperature. However
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, the examples reported so far did not show ferromagnetic behavior at room temperature.
From the viewpoint of their practical application to the magnetic recording systems, the ability to fix their magnetic moments such that they still exhibit room temperature ferromagnetism is an absolute requirement. Here we have designed reversible photo-switchable ferromagnetic FePt nanoparticles whose surfaces were coated with azobenzene derivatized ligands. These composite nanoparticles showed ferromagnetic behavior even at room temperature. On the surfaces of core particles, reversible photoisomerization of azobenzene in the solid state was realized by using spacer ligands which provide sufficient free volume between azo-ligands. These photoisomerization brought changes in the electrostatic field around the core-FePt nanoparticles. As a result, we have succeeded in controlling the magnetic properties of these ferromagnetic composite nanoparticles by alternating photoillumination in the solid state at room temperature. Less
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