Polycrystalline samples of FeMo4Ge3 have been synthesized by the reduction of an oxide mixture at 1248 K and characterized by a combination of diffraction, muon spin relaxation (µ+SR), Mössbauer spectroscopy, magnetometry, transport, and heat-capacity measurements. The compound adopts a tetragonal W5Si3 structure (space group I4/mcm); the iron and molybdenum atoms are disordered over two crystallographic sites, 16k and either 4a or 4b. The synthesis conditions determine which fourfold site is selected; occupation of either leads to the presence of one-dimensional chains of transition metals in the structure. In both cases, the electrical resistivity below 200 K is ~175 µΩ cm. The dc magnetization rapidly rises below 35 K (Fe/Mo on 16k and 4b sites) or 16 K (16k and 4a sites), and a magnetization of 1µB or 0.8µB per Fe atom is observed in 4 T at 2 K. The ac susceptibility and the heat capacity both suggest that these are glasslike magnetic transitions, although the transition shows a more complex temperature dependence (with two maxima in χ") when the 4b sites are partially occupied by iron. No long-range magnetic order is thought to be present at 5 K in either structural form; this has been proven by neutron diffraction and µ+SR for the case when Fe and Mo occupy the 16k and 4b sites.
P. J. Baker et al., "Synthesis and Characterization of Two Metallic Spin-glass Phases of FeMo4Ge3," Physical Review B - Condensed Matter and Materials Physics, vol. 77, no. 13, American Physical Society (APS), Apr 2008.
The definitive version is available at http://dx.doi.org/10.1103/PhysRevB.77.134405
National Science Foundation of Belgium
Keywords and Phrases
Mössbauer Spectroscopy; Diffraction; Heat Capacity; Magnetometry; Muon Spin Relaxation; Polycrystalline
International Standard Serial Number (ISSN)
Article - Journal
© 2008 American Physical Society (APS), All rights reserved.