Theory of hyperfine interactions associated with the negative muon in lanthanum copper oxide high T_c system

We have carried out first-principles Unrestricted Hartree-Fock Cluster investigations to demonstrate that the Auger holes produced by the entry of μ^- into the oxygen ions in La₂CuO₄ lead to stable O^- μ^- centers at apical and planar sites. The hyperfine fields associated with these two sites suggest that the apical one is responsible for the stronger and more anisotropic Knight shift in μSR measurements and the planar for the weaker and less anisotropic shift, the needed susceptibility arising from the localized magnetic moments on the O^- μ^- centers. This identification of the susceptibility provides support for the model proposed for the observed increase in μSR relaxation rate below the superconducting temperatures.