9-13 July 2012
Africa/Johannesburg timezone
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Spin density wave behaviour in the (Cr84Re16)100-yVy system

Presented by Mrs. Bincy Susan JACOBS on 11 Jul 2012 from 08:40 to 09:00
Type: Oral Presentation
Session: DCMPM2
Track: Track A - Division for Condensed Matter Physics and Materials

Abstract

The spin density wave (SDW) behaviour in the (Cr<sub>84</sub>Re<sub>16</sub>)<sub>100-y</sub>V<sub>y</sub> alloy system, with 4 ≤ y ≤ 14, was investigated using electrical resistivity (ρ), Seebeck coefficient (S) and specific heat (Cp) measurements as a function of temperature (T). For this alloy series ρ measurements reveal a clear anomaly at the Néel temperature (T<sub>N</sub>), which can be ascribed to the opening up of the SDW energy gap and the corresponding decrease in charge carrier density on cooling through T<sub>N</sub> [1]. The Seebeck coefficient is sensitive to the changes in the electronic structure and scattering mechanisms that are consequential to the antiferromagnetic phase [1]. An anomaly in the form of a hump in the vicinity of T<sub>N</sub> is observed in the S(T) curves for samples with y = 5.7 and 8.5. On increasing y the magnitude of this anomaly is suppressed and the position of the hump shifts to lower temperatures, corresponding to a decrease in T<sub>N</sub>. At low temperatures, a broad valley is observed for y = 4 and 5.7. On increasing y, this valley initially becomes more pronounced, but eventually weakens and becomes imperceptible in samples with y > 5.7. T<sub>N</sub>(y) obtained from both ρ(T) and S(T) measurements indicate the existence of a possible quantum critical point at y ≈ 10.4. Signatures of quantum critical behaviour have also been linked to anomalies in the behaviour of the Sommerfeld electronic specific heat coefficient (γ) as a function of the tuning parameter [2]. γ is obtained from the low temperature Cp measurements and γ(y) for the (Cr<sub>84</sub>Re<sub>16</sub>)<sub>100-y</sub>V<sub>y</sub> alloy system also shows an anomaly in the vicinity of the putative quantum critical point. [1] E. Fawcett et al., Rev. Mod. Phys. 66, 25 (1994). [2] J. Takeuchi et al., J. Phys. Soc. Jpn. 49, 508 (1980)

Award

Yes

Level

PhD

Supervisor

Prof ARE Prinsloo, alettap@uj.ac.za, University Of Johannesburg

Paper

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