ICAM Themes
Professor Ivan Schuller
University of California at San Diego
Physics Department
9500 Gilman Drive, Mail 0319
La Jolla, CA 92093
(619) 534-2540
(619) 534-0173 FAX
The aim that Condensed Matter Physics-Materials Science is taking at this moment is into two directions; more complex materials and/or materials in reduced dimensionality. In fact, in many cases the same type of phenomena occur in both types of systems because strong electron correlations may be the controlling factor of the properties of complex or materials in reduced dimensions.
The preparation of hard matter in reduced dimensions is both a technically as well as theoretically challenging problem. Preparation techniques (thin film and lithography) are at a stage when one can envision the preparation of an artificial solid made out of small clusters placed at will in three dimensional structures. Quasi one dimensional structures prepared by thin film techniques, with control down to ~10 Å, such as superlattices allow investigation of phenomena in quasi-one dimensions (i.e. two dimensional planes repeated along one direction). Two dimensional structures prepared using sophisticated lithography, with individual entities ( ~100Å) placed in a variety of crystal structures are currently being investigated for their magnetic, transport and superconducting properties. Improvements in the preparation technology is being actively pursued. Quantitative analysis of chemical, physical and spin structure is also being improved to reduce their resolution limits. Sensing the physical properties of these structures is a major problem since the amount of material available is microscopic. Techniques such as light scattering, magnetotransport, local magnetic probes (MFM, scanning SQUID microscopy, scanning Kerr effect), more global magnetic measurements ( neutron scattering, synchrotron radiation) are also being applied and used to investigate the physical properties of these materials.
To date much new physics has been obtained from these types of structures including Giant and Collosal Magnetoresistance, collective superconducting pinning, superlattice effects in the magnons, spin transport across interfaces, novel coexisting phases etc. Moreover these structures have also been giving rise to important applications in the sensor and recording industries. Much more will surely arise.
In the area of complex materials one important aspect is the systematic search for new materials. Unfortunately theoretical methods have been not very useful in guiding the discovery of materials with new unique properties. This has been more or less guided by trial and error. In recent years several new methods have been developed to improve on the systematic search for novel materials using Combinatorial Chemistry Methods. This methods take basically two forms: a) many samples are prepared in a systematic fashion across a multi phase phase diagram and b) phase spread alloys are prepared in which a whole area in phase space is prepared simultaneously. For both methods, automated measurements methods are necessary in order to be able to explore large areas of phase space for desirable properties. Although these methods have been explored with considerable success in the biological and chemical areas its use in the complex hard materials area has been quite limited to a few groups. A number of areas in which there is no well defined guiding principle for the development of a new material, may considerably benefit from these type of searches. This includes the area of catalysis, corrosion, superconductivity, magnetism, ferroelectricity etc. Uses and further developments of these methods may provide perhaps many new materials with interesting new properties.
In both of these areas it is important to combine the talents from various disciplines including materials science, condensed matter physics, chemists, instrumentation, and measurement scientists. Only a global approach in which these different disciplines interact in a symbiotic fashion will give results. The problems are sufficiently complex that one single discipline will not be able to solve all the problems.
I hope this gives some general ideas in the areas in which I have made some contributions and have some working familiarity. I am sure that many new ideas will arise from the workshop and I am looking forward to its results.