Materials Preparation and Characterization of the Quasi-Two Dimensional Triangular Rare-Earth Magnets Ba6Yb2Ti4O17 and ErMgGaO4

Abstract

Within in this work, I present the successful synthesis of Ba6Yb2Ti4O17 in a powder form. To the best of my knowledge, this is the first instance in which this has been achieved. I also show that single crystal synthesis experiments using the floating zone synthesis (FZS) technique have yet to produce single crystals. The magnetic characterization of Ba6Yb2Ti4O17 powder is also presented. DC susceptibility measurements reveal no spin freezing or ordering down to 0.5K and inverse susceptibility shows antiferromagnetic coupling between spins. A cold neutron scattering experiment was performed at low temperatures with and without an applied magnetic field on Ba6Yb2Ti4O17 powder. This experiment shows the possibility of spinon-like excitations with a band width of approximately 0.3meV, but this is inconclusive due to the signal to noise ratio. The powder averaged g-tensor for Ba6Yb2Ti4O17 was also experimentally estimated to be approximately 2.4. Further work required to complete this study is also discussed. Synthesis of phase pure ErMgGaO4 has yet to be reported in the literature. Here, I show that small amounts of phase pure polycrystalline ErMgGaO4 can be produced using the FZS technique. Through using FZS, 0.85g of phase pure ErMgGaO4 powder was produced and supplemented using 1.26g of ErMgGaO4 powder containing approximately 1% Er3Ga5O12 magnetic impurity. To estimate the effect of this magnetic impurity on the magnetic signatures exhibited by ErMgGaO4, DC susceptibility measurements were performed between 0.5K and 50K. The magnetic impurity in such small quantity was shown to have negligible effect on the bulk ErMgGaO4 magnetic features. Cold neutron scattering conducted on this material revealed a spinon excitation continuum similar to the one observed in YbMgGaO4.[1] Also present at low temperatures was a diffuse elastic magnetic feature that was used to estimate an order parameter for the material. Analysis of this diffuse feature also revealed a Warren line shape, indicative of two dimensional correlations within the Er3+ triangular planes. Analysis of the spinon excitation continuum revealed a gapless spinon continuum overall. Results presented for both Ba6Yb2Ti4O17 and ErMgGaO4 will be discussed and compared to neutron scattering experiments performed on YbMgGaO4