Comparative study on the magnetic excitation spectra of Y123 and La214 high-T_c systems - are the dynamical stripes important?

The magnetic spectra χ″ of YBa₂Cu₃O _6.5 are compared with calculated results by the expression χ(q, ω) = χ⁰(q, ω) / {1 + J(q)χ⁰(q, ω)} with J(q) = J(cos q_xa + cos q_ya). For the proper band parameters and other parameters, we obtained satisfactory agreement between experimental and calculated results without considering dynamical "stripes". The quasi particle broadening has been found to suppress the antiferromagnetic ordering. Effects of the dynamical "stripes" on χ″(q, ω) are clearly visible in La_2-xSr _xCuO₄, which is in clear contrast to the results of YBa₂Cu₃O_6.5.