Anisotropy of the Superconducting Critical Magnetic Field H_c2 of La–M–Cu–O System (M=Sr and Ba)

Results of experimental studies on single crystals of high-Tc oxide superconductors are presented. The anisotropy of the superconducting critical magnetic field Hc2 of (La1-xMx)2CuO4-δ (M=Ba and Sr and x∼0.075) indicates that the ratio of the conductivities along the directions within and perpendicular to the c plane, σ/σ⊥, is of the order of 10². The results show the direct evidence of the two dimensional character of the electron transport. The thermoelectric power of the same crystal of (La1-xSrxCuO4-δ is also shown. Brief comments on the crystal preparation are presented.