ANISOTROPIC ELECTRONIC AND THERMAL TRANSPORT-PROPERTIES OF LIGHTLY OXYGEN-DOPED LA2CUO4+DELTA

We track the systematic variation in magnetic susceptibility (chi), thermal conductivity (kappa), anistropic resistivity (rho), and thermoelectric power (S) of crystalline La2CuO4+delta as a function of light hole doping. The level of hole doping (delta) was carefully varied by anneals under controlled oxygen-partial-pressure performed in such a way that the antiferromagnetic ordering temperature T(N) ranged from 250 to 310 K. chi data indicate that increased oxygen hole doping acts to reduce T(N) below the delta = 0 value of 320 K. Anomalies are present in kappa at T(n) that result from Cu spin fluctuations about the magnetically ordered ground state. Anomalies are also present in rho and S that occur at T(N) for air-annealed samples wherein T(N) = 250 K; when more lightly hole-doped so that T(N) > 250 K, the anomalies in rho and S do not occur at T(N), but instead occur at T < 250 K. In analogy with heavily oxygen-loaded La2CuO4+delta, these transport anomalies may result from phase separation involving the diffusion of non-stoichiometric, excess oxygen.