Talks and Poster Presentations (without Proceedings-Entry):

M. El-Hagary, H. Michor, M. Wind, E. Bauer, G. Hilscher, P. Rogl:
"Low Temperature Properties of LaCo9Si4";
Poster: VIII International Conference on Crystal Chemistry of Intermetallic Compounds, L'viv, Ukraine; 2002-09-25 - 2002-09-28.

English abstract:

M. El-Hagary, H. Michor, E. Bauer, G. Hilscher1 and P. Rogl2
1Institut für Festkörperphysik, TU Wien, A-1040 Wien, Austria
2Institut für Physikalische Chemie, Universität Wien, A-1090 Wien, Austria

Ternary LaCo9+xSi4-x alloys have been reported by Rao et al. [1] to be ferromagnetic (TC > 900 K for x > 0.1) with TC approaching to zero for x ~ 0, where an ordered tetragonal compound LaCo9Si4 is formed [1]. In order to perform a more detailed study on the thermodynamic and transport behaviour in the vicinity of the expected quantum critical point, we prepared LaCo9+xSi4-x with (x = 0.2, 0.1, 0, ?0.1, ?0.2, ?0.5) by high frequency induction melting and subsequent annealing at 1050C. The formation of an ordered ternary compound LaCo9Si4 was confirmed by X-ray diffraction and electron microprobe analysis. The low temperature properties of the solid solution LaCo9+xSi4-x were studied by specific heat, magnetisation and resistivity measurements including high field and high pressure techniques. The vanishing of the ferromagnetic order at about x~0 is confirmed. At this composition, i.e. for the ordered compound LaCo9Si4 we observe a regime of strong spin fluctuations with an enhanced Sommerfeld value and a T2 temperature dependence of the electrical resistivity. A metamagnetic phase transition to the ferromagnetic state can be induced with an externally applied field of about 5T.
[1] G.H. Rao et al., Appl.Phys.Lett. 64 (1994) 1650-1652.

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