8-12 July 2013
Africa/Johannesburg timezone
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Magnetic Phase Diagram of Cr100-xOsxalloys

Presented by Mr. Pius Rodney FERNANDO on 9 Jul 2013 from 10:30 to 10:50
Type: Oral Presentation
Session: DCMPM2
Track: Track A - Division for Condensed Matter Physics and Materials

Abstract

The magnetic phase diagram of Cr<sub>100-<I>x</I> </sub>Os<sub><I>x</I></sub> exhibits a triple point at <I>T</I><sub>L</sub> = 315 K and <I>x</I><sub>L</sub> = 0.14,where the incommensurate (I) spin-density-wave (SDW),commensurate (C) SDW and paramagnetic (P) phases coexist. Previous studies [1,2] focused on measurements around the triple point and concentrations up to <I>x</I> = 2. However, the magnetic phase diagrams [1] of other Cr alloys with group-8 diluents, such as those of Cr-Re and Cr-Ru, show interesting features for <I>x</I> >> <I>x</I><sub>L</sub>.This is indicative of the possible merits of an investigation into the magnetic phase diagram of Cr-Os,specifically at high diluent concentrations. For this purpose, a polycrystalline Cr<sub>100-<I>x</I></sub>Os<sub><I>x</I></sub> alloy series with 2 < <I>x</I> < 22 was prepared. Sample buttons were arc-melted from high quality starting materials and characterized using scanning electron microscopy, electron microprobe analysis and X-ray diffraction. Analyses show that the alloys are homogenous in composition and single-phase for Os diluent concentration up to <I>x</I> = 22. Electrical resistivity (<I>ρ</I>) measurements as function of temperature (<I>T</I>),in the temperature range of 2 K < <I>T</I> < 1100 K, was used to obtain the magnetic transition temperatures of the various alloys. The onset of antiferromagnetism causes large anomalies in the <I>ρ</I> versus <I>T</I> curves, associated with the Néel transition temperatures (<I>T</I><sub>N</sub>)[1]. These results were used to determine the magnetic phase diagram of the Cr<sub>100-<I>x</I></sub>Os<sub><I>x</I></sub> alloy system for <I>x</I> > 2. Present results show that <I>T</I><Sub>N</sub> increases up to 575 K at <I>x</I> = 4, and then decreases for <I>x</I> > 4. This behaviour is similar to that observed for other Cr alloys with group-8 impurities [1].Interestingly, results reveal that the antiferromagnetism in the Cr<sub>100-<I>x</I></sub>Os<sub><I>x</I></sub> alloy system is fully suppressed at <I>x</I> = 13. The present results are interpreted and explained in terms of the theory of Fedders and Martin [3]. [1] Fawcett E, Alberts HL, Galkin VY, Noakes DR and Yakhmi JV 1994 Rev. Mod. Phys. 66 25. [2] Butylenko AK and Nevadcha VV 1982 Sov. Phys. Tech. Phys. 27(1) 102. [3] Fedders PA and Martin PC 1966 Phys. Rev. 143 245.

Award

yes

Level

PhD

Supervisor

ARE Prinsloo, alettap@uj.ac.za, Department of Physics, University of Johannesburg, PO Box 524, Auckland Park, 2006

Paper

Yes

Place

Location: A0-60


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