STRUCTURE AND PROPERTIES OF ALLOYED CHALCOGENIDES WITH THE ThCr2Si2 TYPE STRUCTURE

Abstract

The ThCr2Si2-type structure has proven itself to be an incredibly robust structure type. Its ability to incorporate elements from the majority of the periodic table has earned it the moniker of \The perovskite of intermetallics". This layered structural motif has the nominal formula of AM2X2, where typically, A is an electropositive atom, M is a transition metal, and X is a main group element. They are ordered as a layered structure of layers of two-dimensional MX-n4 edge sharing tetrahedra separated by layers of An+ cations. The wide variety of different compounds that have been characterized with this structure has resulted in almost as wide a variety of properties, including superconductivity. This dissertation demonstrates the affects that having a mixed metal site has on the properties of these compounds. Powder and single crystal samples are prepared for a series of compounds so that these effects can be compared for different X atom chalcogenides. We demonstrate that increasing the bond distances through changing the X atom from sulfur to selenium has a pronounced effect on the magnetic and electrical properties. Possible magnetic structures for KCuMnS2 are proposed for the first time. Different methods at tuning the structure to obtain new compounds are discussed.