Inhomogeneity in complex oxides : probing superconductivity and magnetism with scanning SQUID
Abstract/Contents
- Abstract
- Complex oxides, materials consisting of two or more metals and oxygen, are studied widely in condensed matter physics. Heterostructures made of complex oxides are highly tunable platforms for realizing novel electronic and magnetic states. I used a local mangetic imaging technique, scanning superconducting quantum interference device (SQUID) microscopy, to investigate the role of inhomogeneity in two complex oxide heterostructures. By mapping the diamagnetic susceptibility of superconducting delta-doped SrTiO3 and LaAlO3/SrTiO3 as a function of temperature, I showed that an intrinsic source of inhomogeneity—domains of different orientations of the crystallographic unit cell formed at a structural phase transition—causes the superconducting transition temperature to spatially vary in both materials. Previous scanning SQUID measurements as well as other techniques found magnetism in LaAlO3/SrTiO3. Oxygen vacancies were proposed as a possible source. I measured a series of samples with different levels of oxygen vacancies and, finding no magnetism, set limits that are comparable to or are more stringent than signal sizes previously reported in the literature, placing strong constraints on the role of oxygen vacancies in producing magnetism in LaAlO3/SrTiO3 heterostructures. Both heterostructures that I studied exhibit two-dimensional superconductivity. Pointlike defects have the simplest possible geometry for a defect in two dimensions. I compared susceptibility images of several two-dimensional, complex-oxide-based superconductors to a model for the way in which our scanning SQUID susceptometers image defects in two-dimensional superconductors that are much smaller than the length scales of our sensor and found good agreement.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2017 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Noad, Hilary |
|---|---|
| Associated with | Stanford University, Department of Applied Physics. |
| Primary advisor | Moler, Kathryn A |
| Thesis advisor | Moler, Kathryn A |
| Thesis advisor | Fisher, Ian R. (Ian Randal) |
| Thesis advisor | Kivelson, Steven |
| Advisor | Fisher, Ian R. (Ian Randal) |
| Advisor | Kivelson, Steven |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Hilary Noad. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2017. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2017 by Hilary Noad
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