Measuring Magnetism
ABSTRACT :
Magnetic materials are used all around the world for all sorts of different applications like power generation, data storage, transmission of electricity, motion and location sensors, motors, airport screening, etc. In fact they are indemic to our society. However, how do the properties of these materials vary, and how does one measure those “magnetic†properties or design a material to have a particular magnetic property? This presentation will give an overview of how to measure these things, giving examples of their application to the examination of new technological materials. Also, how do you know that the value of the saturation magnetization in your sample is 3.8 Am2/kg (e.g., 3.8 emu/g) and not actually 3.9 Am2/kg? Or maybe you don’t care. Just because your measurement equipment reads out 3.8 emu/g, can you really believe it? This presentation will also introduce the concept of calibration and “standards,†both physical and computational. As time permits, the presentation will also include a description of two relatively new magnetic characterization tools, one of which was developed at NIST, that can provide unique information about the materials. One of them, the First Order Reversal Curve (FORC) method, enables the characterization of materials made up of composites of things, including particle collections, multiple phases, and regions of different magnetic character. The other tool, the Magneto-Optic Indicator Film (MOIF) technique enables the real time imaging of magnetic domains in a ferromagnet (especially in thin films), so that magnetization dynamics can be studied when a field is applied.
ABOUT THE SPEAKER:
Dr. Robert D. Shull is presently one of the 35 Fellows at the National Institute of Standards and Technology (NIST). He received a B.S. degree in Metallurgy and Materials Science from MIT in 1968, and both M.S. and Ph.D. degrees in Metallurgical Engineering from the University of Illinois at Urbana-Champaign in 1973 and 1976 respectively. After serving a Postdoctoral Fellowship at CALTECH from 1976-1979, he joined the National Bureau of Standards (NBS), now known as NIST. Since joining NIST, he pioneered the area of nanocomposite magnetic refrigerants, rapidly solidified the AlMn alloy in which the first "quasicrystals" were discovered, prepared the first laser-ablated High Tc superconductor, and first proved exchange-biased bilayers reverse their magnetic state asymmetrically. Dr. Shull has co-authored over 200 publications, edited 12 books and special journal issues, holds 4 patents, and presented over 380 talks (310 invited) at professional meetings. One of these papers appeared on the cover of Science magazine [Jan. 8, 1988] and another [Phys. Rev. B36, No. 7 (1987) 4036] received an award for the "Best Paper of the Year" at JHU-APL. Dr. Shull is a Past Chairman of the International Committee on Nanostructured Materials, a charter member of the Nanoscale Science, Engineering and Technology Subcommittee of the NSTC, and was the President of TMS (The Minerals, Metals, and Materials Society) in 2007. He is a Fellow of IEEE, a Fellow of TMS, one of 50 Honorary Members of the Indian Institute of Metals, and the 2009 recipient of the SPIE Nanoengineering Pioneer Award. He is also a son of Dr. Clifford G. Shull, the recipient of the 1994 Nobel Prize in Physics.