Magnetism and Geometric Magnetic Frustration in YbFe2O4-Type and Garnet-Type Compounds

Abstract

Geometric magnetic frustration arises when the crystal structure of a compound

inherently hinders long-range magnetic ordering. As numerous important and unusual

magnetic properties are most easily observed in geometrically frustrated materials,

it is an important topic in solid state chemistry. Frustration often results from a

combination of antiferromagnetic interactions and a triangular lattice structure. This

thesis will discuss geometric magnetic frustration and other magnetic properties in

two structure families which possess a prominent triangular motif.

Chapter 1 serves as an introduction to solid state chemistry as a whole, as well

as introducing magnetic concepts that will be referenced for the remainder of the

work. The main body of the thesis is divided into two parts of four chapters each.

Part I focuses on compounds with the YbFe2O4 structure, while Part II describes the

magnetic properties of several garnet-type materials.

Part I begins with an introduction to the structure and properties of compounds

with the YbFe2O4 structure in Chapter 2, followed by a methodological chapter

describing several methods of crystal growth, including the complex Floating Zone

growth method employed in Chapters 4 and 5. These two chapters discuss the synthesis

and magnetic characterization of the compounds TmMgGaO4 and ErMgGaO4,

respectively.

Chapter 6, the first chapter of Part II, serves as an introduction to the garnet

crystal structure, which occurs in many naturally-occurring minerals. Chapter 7 discusses

the subject of high-pressure synthesis, which is the method used to synthesize

the compounds studied in Chapter 8. Chapter 8 itself is a magnetic study of the

garnet Mn3Fe2Si3O12, as well a comparison to a glassy material of the same nominal

composition. Finally, Chapter 9 is an in-depth magnetic study of a family of

lithium-containing rare earth garnets of the form Li3RE3Te2O12.