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Tuning the Magnetic and Electronic Properties of Ruthenates by Strain and Chemical Pressure.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Tuning the Magnetic and Electronic Properties of Ruthenates by Strain and Chemical Pressure./
Author:	Schreiber, Nathaniel.
Description:	1 online resource (149 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
Subject:	Condensed matter physics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30485753click for full text (PQDT)
ISBN:	9798379711085

Tuning the Magnetic and Electronic Properties of Ruthenates by Strain and Chemical Pressure.
Schreiber, Nathaniel.

Tuning the Magnetic and Electronic Properties of Ruthenates by Strain and Chemical Pressure. - 1 online resource (149 pages)

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

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

Includes bibliographical references

Ruthenium 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.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798379711085Subjects--Topical Terms:

3173567
Condensed matter physics.
Subjects--Index Terms:

MagnetismIndex Terms--Genre/Form:

542853
Electronic books.

Tuning the Magnetic and Electronic Properties of Ruthenates by Strain and Chemical Pressure.
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245 1 0 $a Tuning the Magnetic and Electronic Properties of Ruthenates by Strain and Chemical Pressure.
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504 $a Includes bibliographical references
520 $a Ruthenium 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.
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538 $a Mode of access: World Wide Web
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650 4 $a Materials science. $3 543314
650 4 $a Physical chemistry. $3 1981412
653 $a Magnetism
653 $a Molecular-beam epitaxy
653 $a Oxide materials
653 $a Perovskites
653 $a Ruthenium oxide
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690 $a 0794
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710 2 $a Cornell University. $b Materials Science and Engineering. $3 3547480
773 0 $t Dissertations Abstracts International $g 84-12B.
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30485753 $z click for full text (PQDT)