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SQUID-BASED CW NMR SYSTEM FOR MEASURING THE
MAGNETIZATION OF 3He FILMS
by
Kevin Spencer White
A Thesis Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Ful llment of the
Requirements for the Degree
MASTER OF SCIENCE
(PHYSICS)
December 2012
Copyright 2012 Kevin Spencer White
Object Description
| Title | SQUID-based CW NMR system for measuring the magnetization of ³He films |
| Author | White, Kevin Spencer |
| Author email | kwhite@usc.edu;kwhiteusc@gmail.com |
| Degree | Master of Science |
| Document type | Thesis |
| Degree program | Physics |
| School | College of Letters, Arts And Sciences |
| Date defended/completed | 2012-10-24 |
| Date submitted | 2012-11-26 |
| Date approved | 2012-11-27 |
| Restricted until | 2012-11-27 |
| Date published | 2012-11-27 |
| Advisor (committee chair) | Bozler, Hans |
| Advisor (committee member) |
Gould, Chris Hass, Stephan |
| Abstract | This thesis describes the design and construction of a SQUID-based CW NMR system together with its application in a study of the two dimensional magnetism of ³He. ❧ ³He provides an exemplary system for the study of two-dimensional magnetism. Two-dimensional 3He films of varying coverages may be formed by plating ³He on relatively uniform two-dimensional substrates, such as GTA Grafoil and ZYX graphite substrates. At coverages above approximately 20 atoms/nm² on these substrates, the second layer of ³He exhibits a strong ferromagnetic ordering tendency. The ferromagnetic ordering presents as a rapid onset of measured magnetization that becomes independent of the applied magnetic field as film temperatures approach 1 mK. Very low applied magnetic fields are used to probe the ferromagnetic ordering in order to minimize masking of the measured magnetization and to stay within the available bandwidth of the SQUID. ❧ Commensurate with the ferromagnetic ordering, the NMR linewidth increases dramatically at these coverages and temperatures. An increasing linewidth equates to a short decay time with respect to pulsed NMR probing of the two-dimensional ³He magnetization. The decay times at these coverages and temperatures become so short that they fall below the minimum recovery time necessary for a SQUID-based pulsed NMR system to recover from the relatively large tipping pulse and acquire meaningful data. ❧ To address this problem, we have designed a SQUID-based CW NMR system to leverage as much of an already-existing pulsed NMR system as possible but allow accurate measurement of the rapid onset of ferromagnetic ordering of the ³He films below the approximate 1 mK temperature limit of the pulsed NMR system. |
| Keyword | helium; low-temperature; magnetization; ferromagnetism; quantum; nuclear spin; graphite; two-dimensional; NMR; spectroscopy |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Rights | White, Kevin Spencer |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Archival file | uscthesesreloadpub_Volume6/etd-WhiteKevin-1349.pdf |
Description
| Title | Page 1 |
| Full text | SQUID-BASED CW NMR SYSTEM FOR MEASURING THE MAGNETIZATION OF 3He FILMS by Kevin Spencer White A Thesis Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Ful llment of the Requirements for the Degree MASTER OF SCIENCE (PHYSICS) December 2012 Copyright 2012 Kevin Spencer White |
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