Determination of the Anisotropic Rotational Diffusion Constant of Microcrystals Dispersed in Liquid Medium.

Microcrystals of ErBaCuO suspended in a liquid medium were triaxially aligned by a frequency-modulated magnetic field and allowed a free rotational relaxation after the magnetic field was turned off. In situ X-ray diffraction measurements of the suspension were performed during relaxation, and the temporal change of the orientation fluctuation was monitored via broadening of the diffraction spots. The rotational diffusion constants were determined using the plot of the orientation fluctuation versus the elapsed time of rotational relaxation.