On the relaxation of μ+ SR signal and diffusive neutron scattering in AF phase of HTSC

We consider the antiferromagnetic (AF) state of high-Tc compounds and assume the existence of the localized magnetic two-level systems (TLS) with the relatively small energy E in the AF copper planes, which is compatible with a series of experimental data implying low-energy sale in these systems. It is shown in our previous paper that these TLS are formed, if one accept Aharony et al. suggestion that the small doping results in the holes' localization on the oxygen ions in CuO2 planes. Randomly distributed, these TLS cause partial disorder in the average values of AF copper spins. The manifestation of this effect in the μ+SR experiments and the elastic neutron scattering is discussed. Our results are in a qualitative agreement with the temperature dependence and the magnitude of the line shift and the relaxation rate of μ+SR signal. The elastic diffusive neutron scattering at the small wave-vectors near 2D AF Bragg point (1/2, 1/2, l) and near the point (0, 0, l) is predicted. However, the temperature dependence of this scattering, observed in the experiments with YBa2Cu3O6+x at x=0.38, isn't met by our formulae, obtained for a small doping. It is shown, that μSR data give stronger confidence to the ''frustrated bond' rather and ''frustrated plaquette'' case of the hole localization. (orig.)