Date of Award
Doctor of Philosophy (PhD)
Professor J.E. Greedan
The solid solution Lux Sc(1- x) MnO3 has been prepared for 0.00 ≤ x ≤ 1.00. All members crystallize in space group P 6 3cm . The triangular antiferromagnets form 120° spin structures with Néel temperatures between 91K and 130K. Below TN all samples show evidence of out of plane spin canting. With the exception of LuMnO3 for all compositions an in-plane spin-reorientation transition is found at low temperatures. The chiralities of the magnetic structures were determined from neutron powder diffraction data. In the vicinity of TN 2-dimensional magnetic short range order is found. The solid solution Bax Sr(1- x) LaMnO4 crystallizes in the K2 NiF4 structure, space group I 4/ mmm . The magnetic structures were determined from neutron powder diffraction experiments, where Néel ground states were found for x ≤ 0.20. The magnetic moment magnitude decreases with increasing x. The disappearance of magnetic long range ordering for x > 0.20 is rationalized in terms of intralayer and interlayer magnetic coupling constants. 2-dimensional magnetic short range order is found in the vicinity of the Néel temperatures. Polycrystalline Li4 MgReO6 was prepared and investigated by means of neutron powder diffraction experiments. Li4 MgReO 6 crystallizes in space group C2/m and forms an ordered rock salt structure. The Re6+ sublattice consists of distorted face-sharing tetrahedra. Neutron diffraction, heat capacity, bulk magnetic susceptibility, magnetic relaxation and muon spin relaxation measurements reveal a spin glass ground state with Tf = 12K. The spin glass ground state is rationalized in terms of Li-Mg disorder. At 2.5K all magnetic moments are static.
Bieringer, Mario, "Magnetic frustration in transition metal oxides with triangular, tetrahedral and square planar magnetic sublattices" (2000). Open Access Dissertations and Theses. Paper 1792.