X-ray diffraction patterns of superconducting ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{x}}$ particles which have typical dimensions D<5 μm and do not levitate in an inhomogeneous magnetic field at T<$T_c$ show marked evidence of particle alignment when powder specimens are subjected to a 0.5-T field at T<$T_c$, but reveal random orientation for T>$T_c$. A majority of the particles align preferentially with their antiphase twin boundary planes and a-b planes along the applied field, but a minority align with their b axes along the field.

• Received 30 September 1987

DOI:https://doi.org/10.1103/PhysRevLett.60.744