Date of Award

Summer 8-15-2015

Author's School

Graduate School of Arts and Sciences

Author's Department

Physics

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

At ambient pressure all lanthanide metals order magnetically at temperatures at or below ambient. The magnetic ordering is known to result from the indirect exchange interaction between localized 4f magnetic moments mediated by the surrounding conduction electrons, the so-called Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. With the RKKY interaction the magnetic ordering temperature To is expected to be proportional to the de Gennes factor which is a function of the Landé g factor gJ and the total angular momentum J. For example, Gd has the highest value of To, 292 K, at ambient pressure as it has the largest de Gennes factor of 15.75. Under extreme pressure, however, one anticipates that the 4f state of lanthanides would become unstable leading to exotic physics due to the competition between the RKKY interaction and Kondo screening. Four-point dc electrical resistivity measurements have been carried out on the heavy lanthanides Dy, Tb, and Gd in conjunction with their dilute magnetic alloys Y(Dy), Y(Tb), and Y(Gd) under extreme pressures well above those where their atomic volume collapse occurs, Pvc. Unlike Gd, the results obtained reveal for Dy and Tb a strong deviation from de Gennes scaling in the pressure dependence of To as well as a dramatic suppression of superconductivity in a superconducting Y host, all beginning for pressures just above Pvc. To for Dy and Tb appears to rise well above room temperature at 157 GPa and 141 GPa, respectively. These results provide insight into possible Kondo lattice behavior in Dy and Tb.

Language

English (en)

Chair and Committee

James S Schilling

Committee Members

Mark S Conradi, Sophia E Hayes, Erik A Henriksen, Kater W Murch, Li Yang,

Comments

Permanent URL: https://doi.org/10.7936/K70G3H9F

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