Degree Type

Dissertation

Date of Award

2001

Degree Name

Doctor of Philosophy

Department

Physics and Astronomy

First Advisor

Alan I. Goldman

Abstract

A coherent review on the x-ray resonant exchange scattering and basic recapitulation of phenomenological aspects of magnetic interactions were attempted in this thesis. Further, application of the XRES technique to understand the physical origin of various magnetic structures of TbNi2B2 C, TbCu2Ge2 and GdAgSb2 single crystals were tried as a main effort.;TbNi2B2C orders in a longitudinal spin wave structure below TN = 14.5 K. Concomitant with the magnetic ordering, structural phase transition from tetragonal phase (T > TN) to orthorhombic phase occurred. The modulation direction was resolved to be along the longer axis in the basal plane. The wave vector also showed strong temperature dependence and smooth lock-in transition to tau = 611 with the onset of the ferromagnetism at TWFM ~ 8 K. Tb ion's ferromagnetic component was directly observed by x-ray magnetic circular dichroism experiments. A microscopic model was also constructed to account for the ferromagnetism.;Resonant and nonresonant scatterings on TbCu2Ge2 revealed a spin reorientation. By combining the two techniques together, the direction of the magnetic moment in the basal plane was extracted which displayed moment reorientation from [010] (Tt < T < TN) to the ground state configuration of the [110] direction.;Ab initio magnetic structure determination was made on the GdAgSb2. Taking advantage of the polarization analysis and vector properties of the scattering cross sections, the magnetic moment direction as well as modulation wave vector was determined.

DOI

https://doi.org/10.31274/rtd-180813-12629

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Changyong Song

Language

en

Proquest ID

AAI3003272

File Format

application/pdf

File Size

100 pages

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