MRI: Acquisition of an Imaging Spherical Aberration Corrector and a Lorentz Lens for Magnetic Materials Characterization

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Technical Abstract:In Lorentz transmission electron microscopy, a high-energy electron beam is directed through a magnetic thin foil and the deflections caused by the Lorentz force are analyzed by means of through-focus imaging. The attainable spatial resolution of uncorrected Lorentz instruments is in the range 10-15 nm, due to the large spherical aberration coefficient of the low field Lorentz pole piece. In addition, delocalization effects cause significant image blurring, making quantitative measurements very challenging. Recent developments in aberration correction make it possible to correct the spherical aberration of a Lorentz lens to a value which is sufficiently small to suppress delocalization effects, thereby opening up a completely new observation window on the magnetic nanostructure of materials. In this MRI proposal, we request funding for the acquisition of an imaging spherical aberration corrector and a Lorentz lens for magnetic materials characterization; these components will be added to an existing FEI Titan 80-300 TEM. The corrector and Lorentz lens are crucial to meet the increasing demands of magnetic materials characterization. In state-of-the-art magnetic recording media, for instance, the size of the written bits is comparable to the magnetic resolution of uncorrected Lorentz microscopes, so that it is nearly impossible to obtain high resolution Lorentz images of the magnetic microstructure. The combination of a Lorentz lens and a dedicated corrector will bring the spatial resolution in Lorentz mode down to less than 1 nm, with negligible delocalization effects, thereby enabling for the first time the direct quantitative study of magnetic features at a length scale of around 1 nm. We anticipate that a large number of new scientific results will be obtained on material systems for which these observations were previously impossible. The availability of a corrector and Lorentz lens will impact a large number of research groups within CMU, as well as collaborations with local industry and several national laboratories. Through integration of the corrector training sessions with an existing course on TEM, we will strengthen the education of local and remote students in advanced TEM.Non-Technical Abstract:Since their invention in the 1930s, transmission electron microscopes have suffered from a lens aberration, similar to the aberration suffered by the Hubble space telescope when it was first launched; the images acquired in these instruments are blurred instead of sharp, so that it is difficult to extract reliable information about the objects being studied. The Hubble telescope was repaired by the addition of a corrector lens (essentially a pair of corrective glasses), and, recently, such glasses have also become available for electron microscopes. In this MRI proposal, we request funding for the acquisition of corrector optics for an existing electron microscope located at Carnegie Mellon University, along with a special lens that will enable us to study magnetic materials with very high spatial resolution. Magnetic materials are important in many aspects of today's society, in particular in data storage on magnetic hard drives. The individual data bits on a hard drive are so small, that current electron microscopes cannot obtain sharp images of them. Using the corrector, however, it will become possible to study these bits with an unprecedented clarity; these observations, in turn, will result in further improvements in the density of information that can be stored on a hard disk, and in the reliability of long-term storage. The corrective optics will allow for the generation of a large number of new scientific results on materials for which these observations are currently impossible. The availability of the corrective optics will impact a large number of research groups within CMU, as well as collaborations with local industry and several national laboratories. Through integration of the corrector training sessions with an existing course on electron microscopy, we will strengthen the education of local and remote students in advanced materials characterization methods.