MAGNETIC EXCITATIONS AND EFFECTS OF MAGNETIC-FIELDS ON THE SPIN-PEIERLS TRANSITION IN CUGEO3

We analyze the magnetic excitations of a spin-1/2 antiferromagnetic He isenberg model with alternating nearest-neighbor interactions and unif orm second-neighbor interactions recently proposed to describe the spi n-Peierls transition in CuGeO3. We show that there is good agreement b etween the calculated excitation dispersion relation and the experimen tal one. We have also shown that this model reproduces satisfactorily the experimental results for the magnetization vs magnetic field curve and its saturation value. The model proposed also reproduces qualitat ively some features of the magnetic phase diagram of this compound and the overall behavior of the magnetic specific heat in the presence of applied magnetic fields.