Seminar Fizičkog odsjeka

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@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