Andrew Boothroyd

Abstract:

We report preliminary results of a neutron inelastic scattering study of the magnetic excitations in single-crystal PrBa2Cu3O6+x (x approximate to 0.93). The measurements probe (i) the dispersion of the low-energy crystal field levels of the Pr ion in the low-temperature AFIII magnetic phase and (ii) the Cu optic spin wave mode gap in the AFI magnetic phase. We compare the results with previous measurements made when the same crystal was in an oxygen-deficient state, and thus establish the effect of hole doping on the magnetic excitations.

Abstract:

We report the growth of single crystals of La1-xSrxMnO3 (x = 0.0-0.3) by the floating-zone technique in an image furnace under high argon pressure (6-8 atm). Ail excess of Mn in the polycrystalline starting material was used to compensate for the evaporation during growth. single crystals of diameter 8 mm and length 70 mm have been obtained. The phase purity, composition and quality of the crystals were analysed by X-ray diffraction and electron probe microanalysis. We discuss the effect on the crystal growth of varying the amount of Mn excess and of the composition of the growth atmosphere. We also present magnetization and resistivity data for a few of the samples. (C) 2002 Elsevier Science B.V. All rights reserved.