8-12 July 2013
Africa/Johannesburg timezone
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Magnetic properties of the (Cr100-xAlx)99V1 alloy system

Presented by Mr. Blessed MUCHONO on 9 Jul 2013 from 14:10 to 14:30
Type: Oral Presentation
Session: DCMPM2
Track: Track A - Division for Condensed Matter Physics and Materials

Abstract

The magnetic phase diagram of the Cr<sub>100-<i>x</i></sub>Al<sub><i>x</i></sub> alloy system is unique amongst Cr alloy systems because it exhibits a deep minimum at the triple point concentration <i>x</i><sub>c</sub> ≈ 2, where the incommensurate spin-density-wave (SDW) and commensurate SDW phases coexist with the paramagnetic (P) phase [1]. The interesting properties of this system were previously explored by the addition of 5 at.% Mo to form a (Cr<sub>100-<i>x</i></sub>Al<sub><i>x</i></sub>)<sub>95</sub>Mo<sub>5</sub> alloy system [2]. Antiferromagnetism (AFM) in this system was suppressed to below 4 K in the range 2 ≤ <i>x</i> ≤ 6 [2]. Mo suppresses AFM in Cr and its alloys through electron hole pair breaking effects due to electron scattering [1]. For comparison, the present study investigates the magnetic properties of the Cr<sub>100-<i>x</i></sub>Al<sub><i>x</i></sub> system further through the addition of V. This reduces the AFM in Cr alloys through a mechanism different to that associated with Mo by reducing the electron-to-atom ratio [1]. Electrical resistivity (<i>ρ</i>), Seebeck coefficient (<i>S</i>) and magnetic susceptibility (<i>χ</i>) measurements, as a function of temperature in the range 2 K ≤ <i>T</i> ≤ 390 K, were carried out on the (Cr<sub>100-<i>x</i></sub>Al<sub><i>x</i></sub>)<sub>99</sub>V<sub>1</sub> alloy system, with 0 < <i>x</i> < 7. Néel temperatures (<i>T</i><sub>N</sub>) obtained from all these measurements decrease with Al concentration, disappearing near <i>x</i> ≈ 1.5, again reappearing for <i>x</i> > 4.5. <i>ρ</i>(<i>T</i>) and <i>S</i>(<i>T</i>) for samples with <i>x</i> ≥ 6.1 show smeared anomalies making the determination of <i>T</i><sub>N</sub> difficult. However, these anomalies are sharp in <i>χ</i>(<i>T</i>), proving that it is an important tool in probing AFM in this system. The present results show that the addition of just 1 at.% V to the Cr<sub>100-<i>x</i></sub>Al<sub><i>x</i></sub> alloy system suppresses AFM in the concentration range 1.5 ≤ <i>x</i> ≤ 4.5. This behaviour is similar to that of the (Cr<sub>100-<i>x</i></sub>Al<sub><i>x</i></sub>)<sub>95</sub>Mo<sub>5</sub> alloy system [2]. [1] Fawcett E, Alberts H L, Galkin V Yu, Noakes D R and Yakhmi J V 1994 Rev Mod. Phys. 66 25 [2] Smit P and Alberts H L 1986 J. Phys. F: 16 L191

Award

Yes

Level

PhD

Supervisor

Professor ARE Pronsloo, alettap@uj.ac.za, University of Johannesburg

Paper

Yes

Place

Location: A0-60


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