ANISOTROPIC DECREASE OF THE SPIN-PEIERLS TRANSITION-TEMPERATURE OF CUGEO3 WITH A MAGNETIC-FIELD

The transition temperature of the spin- Peierls transition in single c rystals of the inorganic linear chain compound CuGeO3 is determined in magnetic fields up to 5.5T. A decrease quadratic with the applied fie ld is detected which differs by up to 16 % for different orientations of the magnetic field with respect to the crystal axes. By taking into account the principal g-factors of CU2+ in CuGeO3, a unique value for the magnitude of the decrease is derived which is in good agreement w ith the predictions of the Hartree-Fock theory of Bulaevskii, Budzin a nd Khomskii.