High-Pressure Transport Properties of the Superconducting Spin-Ladder System Sr_<14-x>Ca_xCu_<24>O_<41+〓>

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We report the electrical resistivity, the Hall coefficient, 7?jj, and the rnagnetoresistance, IVIR, atpresstures up to 2.0 GPa, of the spin-ladder conapound Srt,n-.cCa.Cuz,tO,tn?.s, on both a polycrys-tal (r : 13.6) and single crystals (I : 11 and 12), in which strperconductivity has been observedonly in a range of both Ca content (" 11< x< 14) arud presstrre (- 1.5< P<x 8 GPa). Thepresstrre dependence of the 7??j, with positive sign, indicates that carrier density increases withincreasing presstrre and localization of hole carriers at low tenaperature is strbstantially sup-pressed by applying pressure. XVe have also fotrnd that a positive IIVIR, which violates Koh[er'srule. seenas to appear below the tenaperattrre at xvhich a spin gap begins to open and stronglydepends on the tetmperature as well as both on Ca content and applied presstmre, suggesting thatthis IN;IR is closely related to the unobile holes in the spin singlet state.
社団法人日本物理学会の論文
1998-07-15