Growth and magnetic characterization of large R2NiO4+delta (R = Pr, Nd) single crystals

To study the static and dynamic properties of the charge stripe phases in the nickelates by neutron scattering, single crystals are needed with a large volume ( >1 cm(3)). We will report the optimization and growth of large R2NiO4+delta (R = Pr, Nd) crystals by the floating-zone technique in an image furnace. Crack-free single crystals of diameter 8-10 mm and length 8090 mm have been obtained. The phase-purity of the crystals has been checked by powder X-ray diffraction, and information on the crystal quality has been obtained by X-ray and neutron diffraction. We will give an account of our investigations into the conditions needed to obtain the highest quality crystals, and we will discuss the magnetic studies by SQUID magnetometry. (C) 2003 Kluwer Academic Publishers.