Moore's law predicts that magnetic bits of memories will early approach nano-meter sizes. However, there are a number of challenges that may impede the use of nano-sized magnets; some of them are related with intrinsic effects such as superparamagnetism that arises when material size approaches the nano-meter scale. Others are related with extrinsic effects as proximity effects, chemical interdiffusion, or roughness, so that, they must be excluded before addressing a solution to superparamagnetism. This proje ct is dedicated to analyze these key issues for the development of nano-structured magnetic media for high-density memories. The subjects to be studied are:(a) growth of arrays of patterned magnetic media, (b) characterization of the arrays, and (c) development of conceptual ideas that allow to overcome the fundamental limits imposed by their scale. Quantitative characterization tools will be used (x-ray and neutron diffraction, STM, AFM¿) to combine a quantitative study of the interfaces, adequate fabrication methods, and proper choices of materials. Although the solution is not obvious, it will be there if a detailed research is carried out. The solution to the superparamagnetic limitation is more complex. Some few key ideas are needed and fundamental research must be done to ascertain which approach is the most promising. A possible solution that will be investigated at the University of California is to take advantage of the Exchange Bias in antiferromagnetic/ferromagnetic (AF/F) layers, that provides an additional anisotropy to stabilize the magnetization, and can induce the reduction in the superparamagnetic length scale. Thus, magnetic dots made of AF/F bilayers will be prepared to study the possible role of exchange biasing on superparamagnetic onsets. During the second phase of the project at Universidad de Oviedo these studies will be extended to amorphous materials that can present a very soft magnetic behaviour and a well-defined uniaxial anisotropy.
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