THE SYNTHESIS AND STRUCTURE-PROPERTY RELATIONSHIPS OF HIGHLY CORRELATED LANTHANIDE INTERMETALLIC AND OXIDE PHASES
Jasmine N. Millican
Intermetallic lanthanide and oxide phases are of great interest due to the fascinating array of structural features and physical property phenomena, such as heavy fermion behavior, superconductivity, and magnetism, they display. The co-existence of two or more of these exotic physical phenomena make these materials ideal to study quantum critical behavior- a point of instability between two stable states of matter. The synthesis, structure, and/or magnetic behavior of several different classes of materials, such as Ln-M-Ga (Ln = La, Ce; M = Ni, Pd), Yb5Pt9, and Y2-xCexTi2O7, have been studied and characterized using neutron powder diffraction (NPD) experiments. This study highlights several different classes of materials to show the versatility of NPD as a powerful analytical probe. The structures and/or magnetic behavior of these materials, which were obtained from NPD results, will also be elucidated.
The Y2-xCexTi2O7 (x = 0, 0.3394, 0.63) series was investigated to determine how the electrocatalytic reactivity in these materials is affected with the introduction of Ce into the Y2Ti2O7 parent structure. NPD experiments allowed for the accurate determination of the oxygen positions and vacancies in this series of materials. The absence of oxygen deficiencies in the structure was confirmed, and it was determined that the site preference of the Ce3+ atoms is the 16d site, which is also occupied by the Y atoms. The nature of the magnetic behavior in Yb5Pt9, a new material which may lie near a quantum critical point, was also investigated using NPD experiments. NPD results suggest that Yb5Pt9 is a rare example of a ferromagnetic heavy fermion with double phase transitions at 0.6 K and 0.65 K.
In collaboration with J. K. Stalick, J. W. Lynn, M. C. Aronson, and J. Y. Chan
Name: Jasmine N. Millican
Mentor: Judith K. Stalick
Bldg 235, Rm A113
Sigma Xi: self (no); mentor (yes)