8-12 July 2013
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
Track: Track A - Division for Condensed Matter Physics and Materials
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  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>). 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 .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 .  Fawcett E, Alberts HL, Galkin VY, Noakes DR and Yakhmi JV 1994 Rev. Mod. Phys. 66 25.  Butylenko AK and Nevadcha VV 1982 Sov. Phys. Tech. Phys. 27(1) 102.  Fedders PA and Martin PC 1966 Phys. Rev. 143 245.
ARE Prinsloo, firstname.lastname@example.org, Department of Physics, University of Johannesburg, PO Box 524, Auckland Park, 2006