Effects of Ca substitution and the pseudogap on the magnetic properties of Y1-xCaxBa2Cu3O7-delta
The effects of planar hole content, p, on the static magnetic susceptibility, χ(T), of Y1-xCaxBa2Cu3O7-δ polycrystalline samples were investigated over a wide range of Ca (x) and oxygen contents. Non-magnetic Ca, in the 3p state, induces a Curie-like contribution to χ(T) that increases systematically and non-linearly with x but is almost independent of p. We argue that this arises from statistical clusters containing two or more nearest neighbor Ca atoms. We have again found that the pseudogap in the quasiparticle spectral weight appears abruptly below a planar hole content p = 0.190 ± 0.005. PACS numbers: 74.72.Bk, 74.25.Ha, 74.25.Dw, 74.62.Dh