Atomic Origin of Magnetic Hardness in our Best Permanent Magnet
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Date: 09-28-2005
Start Time:
4:00pm
End Time: 5:00pm
Speaker: George Srajer
From:
Argonne National Laboratory, Argonne, IL
Location: Interschool lab - 7th floor - CEPSR
Hosted by:
Center for Integrated Science
Abstract:
After a brief overview of the Advanced Photon Source, the nation’s most
brilliant x-ray source for research, we will discuss the atomic origin
of magnetic hardness in our best permanent magnet – Nd2Fe14B.
Rare-earth (RE) ions dramatically enhance magnetic stability through
the interaction of their anisotropic (4f) electron clouds with the
electric field of surrounding charges. Here we show that the
simultaneous presence of RE ions in dissimilar atomic environments
undermines the intrinsic stability of the highest performance permanent
magnets. Experiments were done by using helicity-dependent resonant
diffraction technique in combination with a digital lock-in detection
scheme that synchronizes the measured x-ray diffracted intensity with
the helicity modulation of the incoming x-ray beam. Our results,
supported by theory, show that unequal neodymium sites in the unit cell
of a neodymium-iron-boron single crystal prefer local magnetic moment
orientations orthogonal to one another, reducing magnetic stability.
These findings highlight the need for manipulating the local atomic
structure around rare-earth ions for complete optimization of future
magnets.
*Work at Argonne was supported by the U.S. Department of Energy Office of Science, under Contract No. W-31-109-ENG-38.