SINGLE-CRYSTAL GROWTH BY THE FLOATING-ZONE METHOD OF A GEOMETRICALLY FRUSTRATED PYROCHLORE ANTIFERROMAGNET, TB2TI2O7

Large, high quality, single crystals of Tb2Ti2O7, have been successful ly grown by the floating zone method under a controlled atmosphere. Cr ystals, approximately 3-5 mm in diameter and up to 20 mm in length. we re grown from a small seed crystal. Several crystals have been charact erised to determine their crystal quality, chemical structure and magn etic properties and these results were compared to those of sintered p olycrystalline pellets. These materials were shown to have the face ce ntred cubic structure, Fd-3m, with a room temperature lattice paramete r a = 10.12(7) Angstrom, when grown in oxygen, and a = 10.13(6) Angstr om, when grown in argon. They are currently of interest as they are co mprised of antiferromagnetically coupled magnetic moments residing on a network of corner-sharing tetrahedra, a system known to display the effects of geometrical frustration. Magnetic susceptibility measuremen ts, with the applied field parallel to the growth direction were perfo rmed on both crystals. Both single crystal and polycrystalline samples showed very similar Curie-Weiss like behaviour down to 5 K, with Curi e-Weiss temperatures, theta(ew) of approximately - 19 K. (C) 1998 Else vier Science B.V. All rights reserved.