Doping n-type carriers by La-substitution for Ba in YBa_2Cu_3O_y system

Abstract

Thus far, there is no cuprate system where both n-type and p-type charge carriers can be doped without changing the crystallographic structure. For studying the electron-hole symmetry in an identical structure, we try to dope n-type carriers to YBa2Cu3Oy system by reducing oxygen content and substituting La3+ ions for Ba2+. Single crystals of La-doped YBa2Cu3Oy are grown by a flux method with Y2O3 crucibles and it is confirmed that La actually substitutes \~13% of Ba. The oxygen content y can be varied between 6.21 and 6.95 by annealing the crystals in an atmosphere with controlled oxygen partial pressure. The in-plane resistivity rho_ab at room temperature was found to increase with decreasing oxygen content y down to 6.32, but interestingly further decrease in y results in a decrease in rho_ab. The most reduced samples with y = 6.21 show rho_ab of ~30 mOhm cm at room temperature, which is as much as seven orders-of-magnitude smaller than the maximum value at y = 6.32. Furthermore, both the Hall coefficient and the Seebeck coefficient of the y = 6.21 samples are found to be negative at room temperatures. The present results demonstrate that the non-doped Mott-insulating state has been crossed upon reducing y and n-type carriers are successfully doped in this material.

4 pages, 4 figures, 1 table, accepted for publication in Phys. Rev. B

References in corpus (2)

• Transport and magnetic properties of GdBaCo_{2}O_{5+x} single crystals: A cobalt oxide with square-lattice CoO_2 planes over a wide range of electron and hole doping
• Intrinsic Hall response of the CuO2 planes in a chain-plane-composite system of YBa2Cu3Oy

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