Materials World Network: Magnetic Nanostructures with Perpendicular Anisotropy

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This Materials World Network project aims at investigating magnetic nanostructures with perpendicular anisotropy, which have fascinating magnetization reversal mechanisms and important technological applications in magnetic recording and spintronics. The network will coordinate research groups at the University of California-Davis (UCD) and National Institute of Standards and Technology (NIST) in the US, and the National Tsing Hua University (NTHU) in Taiwan, with complementary expertise and backgrounds. Systematic studies will be carried out on nanostructures with uniform and/or graded perpendicular anisotropy to probe their depth-dependent magnetic configurations and anisotropy gradient, to study the basic magnetization reversal mechanisms and dynamics, and to examine the effect of decreasing inter-grain exchange coupling. Samples will be synthesized in coordinated efforts by the UCD and NTHU researchers, including continuous thin films, grain-segregated granular films, nanodots and nanowires. For uniform anisotropy nanostructures, the size-dependent magnetization reversal mechanisms and microscopic magnetic memory effects will be studied; simultaneous enhancements of magnetic anisotropy and grain segregation in prototype perpendicular media will be explored by using an intermediate layer. For graded anisotropy nanostructures, polarized neutron reflectometry (PNR) study will be performed at NIST to directly and quantitatively measure the depth-dependent magnetization profile and anisotropy gradient. Scanning electron microscopy with spin polarization analysis (SEMPA) will be used at NIST to image vector magnetization as a function of milling depth; it will probe domain wall assisted reversal in these materials that has been predicted to facilitate both writability and thermal stability.This award is co-funded by the Division of Materials Research and the Office of International Science and Engineering.Understanding and controlling the magnetization reversal mechanisms in magnetic nanostructures with perpendicular anisotropy will have profound technological impacts. The nanostructures under investigation have important applications in perpendicular magnetic recording, graded magnetic media, magnetic random access memory, and other types of spintronic devices. The project brings together a network of researchers from physics and materials science with expertise in synthesis of nanostructures, probe microscopy, magnetic and magneto-optical characterization, and neutron and x-ray scattering. This configuration is ideally suited to promote the project in all its scientific aspects. International collaboration is at the heart of this project. A critical component is the international exchange visits, which will facilitate executions of key experiments, enhance discussions of results and planning of future work. UCD and NTHU students involved will visit each other?s lab, integrate the research efforts, participate in experiments, acquire knowledge and training at NIST and Advanced Light Source, learn the comprehensive set of techniques covering all aspects of the research, and gain valuable cultural experiences.