A. Cassanho

Soft phonon behavior and magnetism at the low temperature structural phase transition of La1.65Nd0.35CuO4

We report a neutron scattering investigation of a La1.65Nd0.35CuO4 single crystal which undergoes a second order structural transition with decreasing temperature from a high temperature orthorhombic phase (space group Bmab) to a distinct low temperature orthorhombic phase (space group Pccn) atTs=76 K. The transition is induced by the softening of the phonon mode that involves rotations of the tilt axis of the CuO6 octahedra. Antiferromagnetic long range order is established belowTN=316 K, and a hysteretic reorientation to a noncollinear spin structure occurs belowTs. The low energy spin dynamics of La1.65Nd0.35CuO4 aboveTs are closely similar to those of stoichiometric La2CuO4; at 100 K the gaps for in-plane and out-of-plane polarized spin waves are 2.3 meV and 5 meV, respectively. Out-of-plane polarized magnons are little affected by the structural transition, but the gap for in-plane polarized magnons increases markedly belowTs.

Growth of single crystals of pure and Ce-doped Nd2CuO4

Abstract Single crystals of Nd 2 CuO 4 have been grown from excess CuO by a top seeded solution growth technique. Ce-doped Nd 2 CuO 4 platelet-like single crystals have also been grown by slow cooling of the melt with nucleation sites provided by a platinum wire.

Thermal conductivity of single crystal lanthanum cuprates at very low temperature

Abstract We have undertaken a study of the thermal conductivity of single crystals of pure and strontium doped lanthanum copper oxide in the temperature range 0.1–6 K. For in plane conduction, all samples show approximately a T 2.7 dependence, whereas for conduction across the planes for x = 0 we observe κ ∼ T 2 . This suggests that dimensionality may play an important role in the lattice heat conduction properties of these materials at very low temperature.

Electron-phonon relaxation rate in single-crystal lanthanum cuprate

We report the results of phonon relaxation processes obtained from picosecond transient thermoreflectance measurements of single‐crystal La2CuO4+y (y∼0.06). Nonequilibrium heating was found to occur on a picosecond time scale. The time scale of the nonequilibrium heating is a sensitive measurement of the modest electron‐phonon interaction (λ≤0.1) in the nonsuperconducting La2CuO4+y.

Investigation of the growth of neighborite, NaMgF3

Neighborite, NaMgF 3 , was grown to be used as substrate for high temperature superconductor thin films. The high temperature phase transitions introduce twinning in this crystal. A detailed discussion of the growth conditions and the nature and orientation of the twins are reported.

Growth of large pure, doped and co-doped La2CuO4 single crystals

La 2 CuO 4 single crystals doped with Sr, Ba, Nd and Zn as well as co-doped Sr, Nd have been grown by the top-seeded solution growth technique. In very low gradients, crystals of very good quality could be grown up to 3 cm 3 but had small amounts of flux inclusions. Higher thermal gradients have produced high quality, large area, crack-free crystals. Crystals were grown along the tetragonal (100) and (001) directions in low as well as larger thermal gradients