Multifunctional Magnetic Materials

One of the most attractive features of a molecular approach to magnetism is the modular approach to synthesis, whereby more than one 

6 Much further detailed study and comparison of these materi- 

To date, a relatively small number of materials have been explored in a molecular spintronics device and much remains to be understood. For example, the couphng between the molecular layer and the magnetic electrodes is believed to play a very significant role due to the discrete nature of the molecule s HOMO and LUMO, in contrast to the band properties inherent in a continuous-lattice material. The energies of the frontier orbitals with respect to the Fermi level of the electrodes, the broadening of the frontier orbitals into (narrow) bands and the orientation-dependent orbital overlap between molecule and electrode will all contribute to the transport of spins across the interface. Study of the magnetic properties of molecule surface systems is, therefore, highly important and may also lead to new types of spintronic devices. 

In more recent times, the field has increasingly focused on topics where molecular materials have an advantage over continuous-lattice solids. Such studies can exploit the modular synthesis of molecular materials, whereby different molecules with differing functions can be combined to form a hybrid material with interacting magnetic and/or conducting and/ or optical properties. This is leading to new fields such as molecular spintronics, multifunctional and switchable materials where 

Yokogawa, S. Yasuzuka, K. Murata and T. Mori, Inorg. Chem., 45, 5712-5714 (2006). 

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Furthermore, metals present additional intrinsic properties, such as redox reversibility, magnetism and luminescence. It is, therefore, possible to take benefit from these peculiarities for the design of redox-controlled NLO switches as illustrated in this chapter or for the elaboration of materials combining two or more properties. This latter field of research is in its infancy but it is possible to anticipate many improvements in the future for the elaboration of multifunctional molecular material optimising simultaneously all the wonderful capacities of metals. 

Multifunctional materials are capable of providing two or more primary functions either in a simultaneous manner or sequentially. For instance, multifunctional structural materials exhibit additional functions beyond their basic mechanical strength or stiffness (which are typical attributes of structural materials). Thus, they can be designed to possess incorporated electrical, magnetic, optical, sensing, power generative, or other functionalities, which work in a synergistic manner [1]. 

Polymer latex nanoparticles can be prepared in many materials such as polystyrene and acrylate with controllable size, through radical-initiated polymerization in heterogeneous media (Figure 14.2). The sizes of latex nanoparticles are very dependent on the polymerization conditions. To yield nanosized particles, the polymerization is usually carried out in miaoemulsions [34], For some applications, two or more monomers are used. For example, for polystyrene nanoparticles, divinylbenzene (DVB) is used as a cross-linker to improve the structural performance [35] and methacrylic acid (MAA) or methacrylate (MMA) is used as a co-monomer to provide the nanoparticles with desirable surface chemistry [36,37], Furthermore, some fluorochromes or magnetic materials are incorporated into polymer nanoparticles, to render the particles multifunctional [38,39],... 

Debra Rolison (right) was born in Sioux City, Iowa in 1954. She received a B.S. in Chemistry from Florida Atlantic University in 1975 and a Ph.D. in Chemistry from the University of North Carolina at Chapel Hill in 1980 under the direction of Prof. Royce W. Murray. She joined the Naval Research Laboratory as a research chemist in 1980 and currently heads the Advanced Electrochemical Materials section. She is also an Adjunct Professor of Chemistry at the University of Utah. Her research at the NRL focuses on multifunctional nanoarchitectures, with special emphasis on new nanostructured materials for catalytic chemistries, energy storage and conversion, biomolecular composites, porous magnets, and sensors. 

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