[seminar] Seminar FO, Prof. Michael Reissner

[hbuljan at phy.hr]

Poštovani kolege,

u ponedjeljak 29.10. s početkom u 14.15 sati Prof. Dr. Michael Reissner
sa Tehničkog sveučilišta u Beču (Technische Universitaet Wien) održat će
seminar naslovljen "Magnetic and Mössbauer Investigation of Crystalline
and Quasicrystalline Al3(Mn,Fe) Taylor phases". Seminar će se održati u
sobi F201 na Fizičkom odsjeku, a sažetak se nalazi u nastavku poruke.
Profesor Reissner gostuje na Fizičkom odsjeku PMF-a u sklopu
hrvatsko-austrijskog projekta bilateralne znanstvene suradnje
(voditelji D.Pajić - FO-PMF i M.Reissner - TuWien).

Srdačan pozdrav,
Hrvoje Buljan

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Magnetic and Mössbauer Investigation of Crystalline and Quasicrystalline
Al3(Mn,Fe) Taylor phases

K. Ali (1), M. Reissner (1)*, W. Steiner (1), M.Feuerbacher (2)

(1) Institute of Solid State Physics, Vienna University of Technology,
Wien, Austria
(2) Institut für Mikrostrukturforschung, Forschungszentrum Jülich,
Jülich, Germany

E-mail: reissner at ifp.tuwien.ac.at

57Fe Mössbauer and magnetic measurements are reported on Taylor-phase
compounds T-Al3(Mn,Fe), which can be seen as complex metallic alloys.
The orthorhombic unit cell contains 156 atoms. These investigations
further are extended to Al71Mn19Fe10 crystallizing as decagonal
quasicrystal. Common for both structures are layers, which are oriented
perpendicular to the b-axis in the crystalline or to the periodic axis
in the quasicrystalline compound, allowing the formation of
characteristic building blocks. At low temperatures for all samples spin
glass behavior is observed with freezing temperatures Tf increasing with
Fe content. Above Tf the 57Fe Mössbauer spectra were analysed by a
superposition of two subspectra with intensity ratio around 75:25, which
can be allocated to Fe substituted on Mn sites surrounded either by Al
and Mn or solely by Al with Mn only at the edge of the nearest neighbour
shell. For both subspectra quadrupole splitting and center shift does
not change significantly with Fe content and with structure. Below Tf
broad hyperfine field distributions
with non-vanishing contributions at zero hyperfine field are present.
Magnetic and electrostatic hyperfine interactions are governed by length
scales which are determined by the very similar interatomic
configurations forming the T-Al3Mn phase as well as the decagonal
compound. Presence of long range atomic order is of less importance.

Keywords: quasicrystals, spin glasses, magnetic measurements, Mössbauer
spectroscopy

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