7-11 July 2014
Africa/Johannesburg timezone
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Magnetic and transport studies on Cr100-xIrx alloy single crystals

Presented by Mr. Pius Rodney FERNANDO on 9 Jul 2014 from 17:10 to 19:00
Type: Poster Presentation
Session: Poster2
Track: Track A - Division for Physics of Condensed Matter and Materials
Board #: A.54

Abstract

An investigation of the physical properties of Cr<sub>100-<i>x</i></sub>Ir<sub><i>x</i></sub> alloy single crystals, with <i>x</i> = 0.7, 1.5, 2.0 and 2.5, were previously used to establish the magnetic phase diagram of Cr<sub>100-<i>x</i></sub>Ir<sub><i>x</i></sub> alloy system around triple point concentration [1] where the various magnetic phases co-exist. The present study extends these results by considering the temperature (<i>T</i>) dependence of the Seebeck coefficient (<i>S</i>), specific heat (<i>C</i><sub>p</sub>) and Hall coefficient (<i>R</i><sub>H</sub>) measurements, in addition to the electrical resistivity (<i>ρ</i>) [1]. Well defined anomalies were observed in the electrical resistivity <i>ρ</i>(<i>T</i>) curves of all the samples, due to the antiferromagnetic to paramagnetic phase transition on heating through the Néel temperature (<i>T</i><sub>N</sub>). The <i>S</i>(<i>T</i>) curves of the samples with <i>x</i> = 0.7, 1.5 and 2.0 also exhibit anomalies associated with <i>T</i><sub>N</sub> in the temperature range below 380 K. As the upper limit of temperature for the measurements was 380 K, the anomaly associated with <i>T</i><sub>N</sub> could not be observed for <i>x</i> = 2.5 alloy (<i>T</i><sub>N</sub> = 391.5 K). Contrary to what is normally expected [2] it is noted that the anomaly related to <i>T</i><sub>N</sub> is more prominent in the (<i>ρ</i>) curves than in the <i>S</i>(<i>T</i>) curves. (<i>R</i><sub>H</sub>) measurements carried out from 380 K down to 2 K in a constant magnetic field of 6 T, shows only weak anomalies at <i>T</i><sub>N</sub> for certain samples. The Sommerfeld coefficient (<i>γ</i>) is obtained by fitting <i>C</i><sub>p</sub>/<i>T</i> = γ + (<i>β</i>)<i>T</i><sup>2</sup> to the low temperature <i>C</i><sub>p</sub>/<i>T</i> versus <i>T</i><sup>2</sup> data. The <i>γ</i> values found for the present single crystal samples fits in well with the <i>γ</i> versus electron-to-atom (<i>e</i>/<i>a</i>) ratio curve previously published [3, 4] for certain Cr alloys. [1].Martynova J <i>et al.</i> 1998 J. Magn. Magn. Mat 187 345 [2].Fawcett E <i>et al.</i>1994 Rev. Mod. Phys. 66 25 [3].Heiniger F 1966 Phys. Kondens. Materie 5 285 [4].Heiniger F <i>et al.</i> 1966 Phys. Kondens. Materie 5 243

Award

Yes

Level

PhD

Supervisor

ARE Prinsloo alettap@uj.ac.za

Paper

Yes

Place

Room: D Ring ground level


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