SAIP 2011

Intermediate valence and antiferromagnetic Kondo lattice behaviour in Ce(Au_1-xNi_x)₂Si₂.

14 Jul 2011, 13:45

15m

Parthenon

Oral Presentation Track A - Condensed Matter Physics and Material Science CMPMS1

Speaker

Prof. Moise Bertin Tchoula Tchokonte (University of the Western Cape)

Description

The transition from intermediate valence (IV) behaviour in CeNi₂Si₂ to magnetically ordered Kondo lattice behaviour in CeAu₂Si₂ is investigated through measurements of X-ray diffraction (XRD), electrical resistivity &rho(T), magnetization &sigma(µ0H) and magnetic susceptibility &chi(T) on the polycrystalline Ce(Au_1-xNi_x)₂Si₂ (0 ≤ x ≤ 1) alloy series. Lattice parameters as derived from XRD measurements deviate from Vegard’s rule around x = 0.6 – 0.8. &rho(T) data indicate Kondo lattice behavior in the presence of a crystal field for x ≤ 0.6, the occurrence of magnetic ordering for x = 0 and fluctuating valency for x ≥ 0.8. &chi(T) data at high temperatures, follow the Curie-Weiss relation for alloys in the concentration 0 ≤ x ≤ 0.6 (Kondo lattice region) and give effective magnetic moment values µ_eff close to that expected for the free Ce³⁺-ion. The low temperature &chi(T) data indicate the onset of antiferromagnetic ordering for x ≤ 0.78. For alloys in the concentration range 0.8 ≤ x ≤ 1 (IV region), &chi(T) data are described within the framework of the paramagnon model. &sigma(µ₀H) measurements indicate metamagnetic behavior for alloys in the concentration range 0 ≤ x ≤ 0.1.