セガワ コウジ   SEGAWA KOJI
  瀬川 耕司
   所属   京都産業大学  理学部 物理科学科
   職種   教授
言語種別 英語
発行・発表の年月 2006/09
形態種別 研究論文
標題 Doping n-type carriers by La substitution for Ba in the YBa2Cu3Oy system
執筆形態 その他
掲載誌名 PHYSICAL REVIEW B
出版社・発行元 AMERICAN PHYSICAL SOC
巻・号・頁 74(10)
著者・共著者 Kouji Segawa,Yoichi Ando
概要 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 similar to 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 similar to 30 m Omega 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 nondoped Mott-insulating state has been crossed upon reducing y and n-type carriers are successfully doped in this material.
DOI 10.1103/PhysRevB.74.100508
ISSN 1098-0121
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