Plenarvorträge - DPG-Tagungen

Metallphysik Dienstag
As has been known for more than fourty years, rare-earth dihydrides
like LaH2.0 are metals and the trihydrides (LaH3.0) are semiconductors.
The metal-non-metal transition of the LaHx-system was first observed in
1957 [1]. Shinar et al. ([2] 1990) determined the transition concentration
to x=2.86. Whereas it is well known that band filling and atomic order
play a significant role in this transition, important aspects are currently
not understood. Recent interest in this field dates from the observation
that rare-earth hydride mirrors can be switched reversibly from reflectivity
to transparency for visible light via the hydrogen content. We carried
out measurements of the Pauli-susceptiblility, the 139 La Knight-shift and
the 139 La spin-lattice relaxation rate in order to obtain the concentration
M 19 Hauptvortrag Jorg Wiezorek
dependence of the electronic density of states at the Fermi-level (DOS).
These results are compared with earlier NMR [3] and specific-heat [4]
data. We thank R. Barnes and G. Majer for disposal of samples.
[1] B. Stalinski, Bull. Acad. Pol. Sci. Cl.III 5, 1001 (1957)
[2] J. Shinar, B. Dehner, R. G. Barnes and B. J. Beaudry, Phys. Rev.
Lett. 64, 563 (1990)
[3] R. G. Barnes, C. T. Chang, G. Majer, U. Kaess, J. Alloys Compounds
137, 356-357 (2003)
[4] K. Kai, K. A. Gschneidner, Jr., B. J. Beaudry, D. T. Peterson, Phys.
Rev. B 40, 6591 (1989)
Zeit: Mittwoch 14:00–14:30 Raum: H16
Hauptvortrag M 19.1 Mi 14:00 H16
Combined Reaction Processing of Fe-Pd based Ferromagnetic
Intermetallics — •Jorg Wiezorek — UPitt: MSE, University of
Pittsburgh, 848 Benedum Hall, Pittsburgh, PA 15261, USA
Jörg M.K. Wiezorek Department of Materials Science and Engineering,
University of Pittsburgh, 848 Benedum Hall, Pittsburgh, PA, USA.
Alloys based on Fe and Pd are of interest for permanent magnet applications
due to the large uniaxial magnetocrystalline anisotropy associated
with the formation of the L1o-ordered intermetallic phase, gamma1-
FePd. However, the magnetic properties of FePd after conventional processing
are disappointing. Optimization of the technical properties of
M 20 Nanoskalige Materialien I
FePd ferromagnets requires the development of a detailed understanding
of the phase-transformation and microstructural transformation behavior.
Here, thermo-mechanical processing, termed combined reaction
(CR) processing, was used to control microstructural scale and morphology
and to improve the properties of FePd. CR processing exploits the
interplay between recrystallization and the ordering transformation during
annealing after cold-work at T