Neutron Scattering Studies of La2_xBaxCuO4

Abstract

<p>Elastic neutron scattering studies have been performed on high quality single crystal samples of lightly doped La_{2_x}Ba_xCuO₄ 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 T_N ~ 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 La_{2_x}Sr_xCuO₄.[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.</p>