SAIP2022

Hall Coefficient of (Cr100-xAlx)95Mo5 Alloy System

Not scheduled

2h 30m

Zoom Platform (Virtual Conference)

Poster Presentation Track A - Physics of Condensed Matter and Materials Poster Session

Speakers

Dr B Muchono (University of Eswatini) Blessed Muchono (University of Johannesburg)

Description

Hall coefficient (R_H) measurements have shown to be an effective method in determining the number density, n=(qR_H)^-1, and the type of majority charge carriers at the Fermi surface (FS) [1-3] of Cr and its alloys. Parts of the Fermi surface sheets that are annihilated during antiferromagnetic (AFM) ordering in Cr based alloys have large effects on the number density resulting in an anomalous behaviour on cooling below the Néel transition temperature, T_N [4]. Previous studies on the (Cr_100-xAl_x)₉₅Mo₅ alloy system through electrical resistivity (ρ), Seebeck coefficient (S), thermal conductivity (κ), specific heat C_p , magnetic susceptibility (χ) and neutron diffraction measurements have shown that antiferromagnetism is suppressed in the concentration range 1.4 ≤ x ≤ 4.4 [5]. The present study was undertaken in order to extend the previous findings on this alloy system, through Hall coefficient measurements. R_H of polycrystalline (Cr_100-xAl_x)₉₅Mo₅ alloys was measured over the temperature range 2 K ≤ T ≤ 380 K in a magnetic field of 4.5 T. Anomalies in the form of an upturn were observed just below the T_N for the AFM alloys with x ≤ 1.3 and x ≥ 5.3. In addition to these anomalies, alloys with x = 0, 0.5, 0.9 and 8.6 show a peculiar behaviour below T_N, in which R_H increases and then decreases depicting a hump on further cooling. Remarkably R_H for the alloy with x = 0 shows a sign reversal of majority charge carriers from holes to electrons on cooling below 120 K. The crossover of majority charge carriers disappears by the addition of just 0.6 at.% Al into the alloy with x = 0. The behaviour of alloys with x = 0, 0.5, 0.9 and 8.6 is explained in terms of the two band model in which both charge carriers contribute to magneto-transport properties [6]. The relative magnetic contribution to the Hall coefficient, ΔR_H(2K)/R_H(2K) indicate a suppression of antiferromagnetism in the concentration range 1.7 ≤ x ≤ 4.7.

[1] Jaramillo R, Feng Y, Wang J and Rosenbaum T F 2010 PNAS. 107 13631
[2] Yeh A, Soh Y A, Brooke J, Aeppli G, Rosenbaum T F and Hayden S M 2002 Nature 419 459
[3] Lee M, Hussman A, Rosenbaum T F and Aeppli G 2004 Phys. Rev. Lett 92 187201
[4] Sheppard C J, Prinsloo A R E, Alberts H L, Muchono B and Strydom A M 2014 J. Alloys and Compounds 595 164
[5] Muchono B, Sheppard C J, Venter A M and Prinsloo A R E 2018 Physica B Condens Matter 537 212.
[6] Cox W R, Hayes D J and Brotzen F R 1973 Phy. Rev. B 7 3580

Level for award;(Hons, MSc, PhD, N/A)?

N/A