Date of Award

9-2009

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics

Supervisor

B. D. Gaulin

Language

English

Abstract

Elastic neutron scattering studies have been performed on high quality single crystal samples of lightly doped La2_xBaxCuO4 with concent rations of x=0, 0.006, 0.0125 and 0.025. These samples display x dependent magnetic structures with transition temperatures which closely follow the usual phase diagram for this material. A low temperature, 2D antiferromagnetic transition has been observed in samples with hole concent ration near the 'spin-glass' transition at x~0.02. In data collected on the N5 triple axis spectrometer at Chalk River, the sample with x=0.0125 demonstrates the onset of 3D antiferromagnetism with TN ~ 151K, followed by attenuation of the scattering intensity of the (1/2,1/2,0) magnetic Bragg peak below T=21K, indicating the onset of 2D magnetic ordering. This result is similar to that obtained by Matsuda et al. in lightly doped La2_xSrxCuO4.[1] This result is confirmed by direct observations of 2D 'rods ' of magnetic scattering in time-of-flight measurements performed on the Disk Chopper Spectrometer at NIST.

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