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SMT-Aug2018

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38 SMT007 MAGAZINE I AUGUST 2018 values (undesirable) and cases where high CI values (undesirable) are matched with high final SIR values (desirable). These results indi- cate that CI values and SIR values are not well correlated in all cases. SMT007 Acknowledgements The author would like to thank Dr. Karen Tellefsen for performing the SIR testing and tabulating the results, Michael Previti for help selecting and acquiring the right variety of fluxes to test, and the Quality Lab at UTC Fire & Security in Lincolnton, North Carolina for providing access to a localized cleanliness tester. References 1. Fullerton, Jason, "A Comparison of Local- ized Electronics Cleanliness Testing and Surface Insulation Resistance—Part 1," Proceedings of the International Conference on Soldering and Reliability 2017, SMTA. 2. Foresite Inc., "Operating Manual, Local- ized Electronics Cleanliness Tester and Residue Extractor [Model C3/C.I.]," February 19, 2015. 3. Foresite Inc. "Foresite C3 Corrosivity Index (C.I.)," December 15, 2014. 4. Foresite Inc., "Operating Manual, Local- ized Electronics Cleanliness Tester and Residue Extractor [Model C3/C.I.]." 5. Foresite Inc. "Foresite C3 Corrosivity Index (C.I.)" Originally published in the proceedings of SMTA International, 2017. Jason Fullerton is a customer technical support engineer at Alpha Assembly Solutions. In a new study published in Physical Review Letters, physicists at EPFL's Institute of Physics have used scanning tunneling microscopy to demonstrate the stability of a magnet consisting of a single atom of holmium, an element they have been working with for years. The scientists exposed the atom to extreme conditions that normally de-magnetize single-atom magnets, such as temperature and high magnetic fields, all of which would pose risks to future storage devices. Using a scanning tunneling microscope, the scientists found that the holmium atoms could retain their magnetization in a magnetic field exceeding 8 Tesla. The authors describe this as "record-breaking coercivity", a term that describes the ability of a magnet to withstand an external magnetic field without becoming demagnetized. Next, the researchers exposed a series of Holmium single-atom magnets to temperatures of up to 45 Kelvin. The Holmium single-atom magnets remained stable up to a temperature of 35K. Only at around 45K, the magnets began to spontaneously align themselves to the applied magnetic field. This showed that they can withstand relatively high temperature perturbations and might point to the way forward for running single- atom magnets at more commercially viable temperatures. "We have demonstrated that the smallest bits can indeed be extremely stable, but next we need to learn how to write information to those bits more effectively to overcome the magnetic 'trilemma' of magnetic recording: stability, writability, and signal-to-noise ratio," says EPFL's Fabian Natterer who is the paper's first author. Source: École Polytechnique Fédérale de Lausanne (EPFL) A Step Closer to Single-Atom Data Storage LEFT: STM image of Holmium single atom magnets. RIGHT: Cobalt helper atoms on magnesium oxide. Credit: F. Natterer/EPFL

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