NMR studies of CuInS2 and CuInSe2 crystals grown by the Bridgman method

Bridgman-grown polycrystalline CuInS2 and CuInSe2 containing 2 at.% excess S and Se, respectively, were investigated by Cu-63 and In-115 NMR. Cu-63 lineshapes were obtained at 79.83 MHz within the temperature range of 123 < T < 473 K, Line-shapes from both samples are similar and are typically broadened by first-order electric quadrupolar interactions with average coupling constant magnitudes of 0.54 MHz; whereas, the central transition reveals broadening due to chemical shift anisotropy. Temperature dependent motional narrowing of the copper line is observed with CuInSe2; the associated diffusion coefficient is 3 x 10(-13) cm(2)/s at 473 K. The dependence of the paramagnetic shift with temperature suggests a complex form of magnetic ordering between unpaired spins. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.