Single crystal growth of the high pressure phase of (VO)2P2O7 at 3 GPa

Single crystals of the high-pressure phase of (VO)(2)P2O7 were grown by slowly cooling the melt at 3 GPa, Relevant reactions at high pressure and high temperature were studied in advance by in situ X-ray diffraction (XRD) measurements, The crystal structure of the high-pressure phase was determined by single-crystal XRD, Magnetic susceptibility of the crystal was measured along the three principal axes and analyzed using a S = 1/2 Heisenberg AF alternating-exchange chain model, A good fit was obtained using the g values determined by ESR measurements, J(1)/k(B) = 131.6(1) K, and an alternation parameter of alpha = J(2)/J(1) = 0.8709(5). The spin gap was estimated to be Delta/k(B) = 33.4(2) K. (C) 2000 Academic Press.