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Investigation of Structural and Magnetic Properties of Perovskite Type Oxides Containing 5d Ions

Xiong, Jie
http://rave.ohiolink.edu/etdc/view?acc_num=osu1492623459123207

Abstract Details

2017, Doctor of Philosophy, Ohio State University, Chemistry.
The focus of this thesis work is to explore the exotic magnetism in perovskite type oxide materials containing 5d transition metal. Strong spin orbit coupling and extended 5d orbitals lay the foundation of unique orbital and spin interactions between 5d ions. Understanding the physics of 5d ions is not only of fundamental interests, but important in the search for new phases of matter such as topological insulators, Weyl semimetals and quantum spin liquids. Chapter 2 and 3 discuss the magnetic behavior of 5d1 and 5d2 ions on a face-centered cubic lattice embedded in the double perovskite structure. The crystal structure, transport and magnetic properties of double perovskites Ba2BReO6 (B=Cd, Zn, Sc, In, Lu, La), Sr2LuReO6 and Ca2ScReO6 are characterized by X-ray diffraction, neutron diffraction, dc electric conductivity, dc magnetometry and heat capacity. Ferromagnetic ground states are prevalent in 5d1 systems. Orbital degree of freedom dominates the magnetic behavior over a wide temperature range before the magnetic ordering, resulting in changing effective moments with temperature and artificial negative Weiss constants. The ground state is a delicate balance sensitive to factors such as spin orbit coupling, metal-oxygen covalency, and subtle structural details. On the other hand, 5d2 systems are dominated by antiferromagnetic ground states. Filling d orbitals on the diamagnetic ion tends to destroy long range magnetic ordering in compounds with cubic symmetry. Strong distortion of the octahedral environment of 5d2 ions can result in ionic singlet states, which is not possible in 5d1 systems. Chapter 4 investigates the superexchange coupling between 5d ions and 3d ions in ordered double perovskites Sr2-xCaxCoOsO6. The crystal structures and magnetic properties are characterized using X-ray diffraction, neutron diffraction and magnetometry. Independent magnetic ordering of Co and Os sublattices are found in Sr-heavy compounds with less structural distortions, stabilized by Co-Co interactions (Co-O-O-Co and Co-O-Os-O-Co superexchange coupling) and Os-Os interactions (Os-O-O-Os and Os-O-Co-O-Os superexchange coupling), respectively. The Os-Os interactions are more sensitive to structural distortions than the Co-Co interactions. As a result, magnetic ordering of the Os sublattice disappear at lower Ca doping level than that of the Co sublattice. The strength of Co-Os superexchange coupling increases as the structure gets more distorted, resulting in ferrimagnetic ordering between Co and Os sublattices on the Ca-heavy compound. Complex glassy behavior is present in a wide compositional range in between due to the presence of competing magnetic interactions.
Patrick Woodward, Prof. (Advisor)
156 p.
Chemistry
Structural and Magnetic Properties; Perovskite Type Oxides Containing 5d Ions

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Citations

  • Xiong, J. (2017). Investigation of Structural and Magnetic Properties of Perovskite Type Oxides Containing 5d Ions [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492623459123207

    APA Style (7th edition)

  • Xiong, Jie. Investigation of Structural and Magnetic Properties of Perovskite Type Oxides Containing 5d Ions. 2017. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1492623459123207.

    MLA Style (8th edition)

  • Xiong, Jie. "Investigation of Structural and Magnetic Properties of Perovskite Type Oxides Containing 5d Ions." Doctoral dissertation, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492623459123207

    Chicago Manual of Style (17th edition)

osu1492623459123207
203
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