Magnitude of spin and charge density wave amplitudes in underdoped cuprates

Self-consistent calculation of spin (charge) density wave (S(C)DW) order parameters have been performed for bilayered cuprates on the basis of a singlet-correlated band model. Evolution of the Fermi surface in the strongly underdoped regime is described by a two-band approach. The smooth development of the pseudogap formation temperature from underdoped to overdoped states is explained and the Fourier amplitudes 〈s_q〉 (spin) and 〈e_q〉 (charge) modulations are calculated. We have found a maximum of the incommensurability for doping 0.09 ÷ 0.11 holes per copper site.