Magnetic correlations in CuGeO₃

The static spin structure factor S(Q) of CuGeO₃ was determined above its spin-Peierls transition temperature by inelastic neutron scattering. At 20 K, S(Q) has a Lorentzian line shape centered at the antiferromagnetic (AF) zone center. With increasing temperature, however, it splits into two peaks with their centers at incommensurate wave vectors at higher temperatures (70 and 120 K). The observed results are consistent with the prediction by recent numerical studies on the S = 1/2 Heisenberg AF chain with competing spin interactions [I. Harada and Y. Aoyama, (1999) "Static spin structure factor of CuGeO₃ above spin-Peierls transition temperature", J. Phys. Chem. Solids 60, 1105; I. Harada, Y. Nishiyama, Y. Aoyama and S. Mori, (2000) "Spin correlation in the one-dimensional Heisenberg antiferromagnet with competing interactions", J. Phys. Soc. Jpn. 69, (Suppl. A), 339].