Molecular Spintronics

Over the last decade there has been tremendous growth in the fields of spintronics and organic electronics. Individually, these fields promise to deal with two aspects of the challenges now facing modern inorganic semiconductor electronics: the first being the need - driven by ever increasing power densities and the quest for quantum computers - to exploit degrees of freedom other than the electron charge; the second being the desire for very cheap, universally printable circuits. Although the term 'spintronics' is relatively new, and refers to the manipulation and measurement of the spin rather than just the charge of the electron, information technology has long depended on the electron spin for data storage. Arguably the first advanced spintronic devices are the magnetoresistive (where an external magnetic field modulates the electrical resistance of a material) read heads which have revolutionised hard-drive data storage. The next major use of spintronics will almost certainly be in magnetic random access memory (MRAM), which will combine many of the advantages (notably access speed) of DRAM with the non-volatility of hard drives.Thanks to their low cost, ease of processing, chemical versatility and compatibility with flexible substrates, molecular semiconductors such as phthalocyanines, porphyrins and perylenes, whose key features are rings of carbon atoms, are establishing themselves as attractive alternatives to inorganic semiconductors, such as silicon, for a variety of optoelectronic devices, e.g. organic light emitting diodes (OLEDs) and photovoltaics (OPV). These materials are extremely versatile, with a long history in biomedicine; indeed chlorophyll (which converts light into energy in plants) is a porphyrin derivative and phthalocyanine derivatives are used in cancer therapy. They also have properties that make them desirable for spintronics. Their long spin relaxation times are already being exploited, for example, in spin valve devices where amorphous organic films are used as spacers. Furthermore, they are endowed with high molecular purity compared to inorganic crystal lattices, and display tremendous flexibility for insertion of magnetic entities into molecular frameworks which can be tailored at will, contrary to what can be attained in gallium arsenide (GaAs), the most widely used inorganic semiconductor material for spintronics. Other major advantages of organic molecules are highly tuneable optical properties and large magneto-optic effects in the visible region of the spectrum, which are compatible with discrete local switching.Our research will develop the new field of molecular spintronics, with the specific aim of creating a platform technology for magneto-optics, electronics, and molecular recognition. The platform will be developed for areas where organics have unique advantages. We look forward to particularly dramatic impacts on biology where functionalization is more straightforward than for inorganics, and for quantum information technology where the separation into magnetic ion and ligand subsystems provides independent addressability of qubits (the magnetic ions which can be positioned at will in the carbon ring centers) and control bits (the overlapping ligand - carbon ring - orbitals) which cannot be readily achieved in inorganic solids. To carry out the programme, we have assembled an interdisciplinary team from London and Warwick which has already combined informally to perform groundbreaking proof of concept work, including the fabrication of phthalocyanine nanowires and observation of highly informative magnetic resonance in molecular thin films, for the current proposal. The project has a very specific set of objectives, ranging from optically controlled magnetic interactions to a novel bioassay chip relying on magnetic resonance. To facilitate management, there will be work-packages for film deposition and characterization, devices, biology and theory.