Measuring the hole-state anisotropy in MgB2 by electron energy-loss spectroscopy
Klie, Robert F.
Davenport, James W.
Browning, Nigel D.
Nellist, Peter D.
Date of Issue2003
School of Materials Science and Engineering
We have examined polycrystalline MgB2 by electron energy-loss spectroscopy (EELS) and density of states calculations. In particular, we have studied two different crystal orientations,  and , with respect to the incident electron beam direction, and found significant changes in the near-edge fine structure of the B K-edge. Density-functional theory suggests that the pre-peak of the B K-edge core loss is composed of a mixture of pxy- and pz-hole states and we will show that these contributions can be distinguished only with an experimental energy resolution better than 0.5 eV. For conventional transmission electron microscope/scanning transmission electron microscope instruments with an energy resolution of ~1.0 eV the pre-peak still contains valuable information about the local charge-carrier concentration that can be probed by core-loss EELS. By considering the scattering momentum transfer for different crystal orientations, it is possible to analytically separate pxy and pz components from the experimental spectra. With careful experiments and analysis, EELS can be a unique tool measuring the superconducting properties of MgB2 , doped with various elements for improved transport properties on a subnanometer scale.
Physical review B
© 2003 American Physical Society. This paper was published in Physical Review B and is made available as an electronic reprint (preprint) with permission of American Physical Society. The paper can be found at: [DOI: http://dx.doi.org/10.1103/PhysRevB.67.144508]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.