자료유형  

 학위논문

Control Number  

0016932058

International Standard Book Number  

9798379711085

Dewey Decimal Classification Number  

530

Main Entry-Personal Name  

Schreiber, Nathaniel.

Publication, Distribution, etc. (Imprint  

[S.l.] : Cornell University., 2023

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2023

Physical Description  

1 online resource(149 p.)

General Note  

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

General Note  

Advisor: Schlom, Darrell.

Dissertation Note  

Thesis (Ph.D.)--Cornell University, 2023.

Restrictions on Access Note  

This item must not be sold to any third party vendors.

Summary, Etc.  

요약Ruthenium oxides, or ruthenates, are an exciting group of materials, which include well-characterized unconventional superconductivity, current-induced metal-insulator transitions, and ferromagnetism. These materials have been studied for decades. However, in this thesis I will demonstrate how traditional thin film tools - absorption-controlled growth, epitaxial strain, and chemical pressure - applied to extensively studied materials can unearth entirely new properties.In the first part of the thesis, I describe how absorption-controlled growth of ruthenates enables the synthesis of nearly perfect thin films. The electronic quality of SrRuO3/DyScO3(110) thin films achieved in this work are record-breaking, with a residual resistivity ratio (RRR) value, p[300 K]/p[4 K], of 205. This high RRR sample revealed the intrinsic Curie temperature (TC) of epitaxially strained SrRuO3/DyScO3(110) to be 168.3 K. This TC is actually enhanced relative to the TC of bulk single crystal samples (TC = 163.5 K). We intentionally grow a series of SrRuO3/DyScO3(110) samples ranging from bad RRR (8.8) to great RRR (205) to show that the bad samples have TCs below the bulk value. Measurements done on poor-quality SrRuO3 thin films can be misleading and even show the opposite result when compared to high-quality samples. Therefore, absorption-controlled growth is an important tool for thin film growers and should be used if possible. Next, I show that the magnetic properties of SrRuO3 can be controllably tuned using calcium substitution. The magnetic easy axis, the TC, the coercive field (Hc), and the anomalous Hall effect (AHE) of SrRuO3 can all be controlled within the CaxSr1-xRuO3/LSAT(100) solid solution. As the calcium concentration is increased, the TC and Hc decrease, the magnetic easy axis goes from entirely out-of-plane to somewhat in-plane to entirely in-plane, and the AHE changes sign from negative to positive. All of these property changes can be used to design novel ruthenate heterostructures because the property changes all occur on compatible materials grown on the same substrate, LSAT(100).In the next part of the thesis, I create one of these potential all-ruthenate heterostructures by combining two layers of opposite AHE sign. The heterostructure settles the debate on whether measurements of the topological Hall effect (THE) provide sufficient evidence to prove the presence of skyrmions in a material. Since I can recreate the "topological Hall" signal without the presence of skyrmions in our samples, I conclude that the THE signal alone is insufficient and that additional measurements are necessary for skyrmion detection. This heterostructure is only one application of the CaxSr1-xRuO3/LSAT(100) magnetic phase diagram, and I expect more exotic heterostructures will be designed in the future.Finally, I present the simplest and, in many ways, most interesting ruthenate material, RuO2. In this part of the thesis, I show that antiferromagnetic RuO2 thin films grown on TiO2 substrates can generate polarized spin currents, which can be used to flip a neighboring ferromagnetic material at room temperature. RuO2 can be grown at low temperatures and it has a large spin torque efficiency, making it suitable for non-volatile memory devices.

Subject Added Entry-Topical Term  

Condensed matter physics.

Subject Added Entry-Topical Term  

Materials science.

Subject Added Entry-Topical Term  

Physical chemistry.

Index Term-Uncontrolled  

Magnetism

Index Term-Uncontrolled  

Molecular-beam epitaxy

Index Term-Uncontrolled  

Oxide materials

Index Term-Uncontrolled  

Perovskites

Index Term-Uncontrolled  

Ruthenium oxide

Added Entry-Corporate Name  

Cornell University Materials Science and Engineering

Host Item Entry  

Dissertations Abstracts International. 84-12B.

Host Item Entry  

Dissertation Abstract International

Electronic Location and Access  

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Control Number  

joongbu:643670