YBa_2Cu_3O_y中对Y位与Cu(Ⅰ)位取代导致的空穴浓度变化

VARIATION OF HOLE CONCENTRATION INDUCED BY ELEMENT SUBSTITUTION AT Y AND Cu(I) SITES IN YBa_2Cu_3O_y SYSTEM

本文研究Co对Cu(I)和Ca对Y作取代时,YBa_2Cu_3O,系统中的空穴浓度、晶体结构和超导临界温度随掺杂量的变化关系及其起源。结果表明,上述取代对体系中的Cu-O平面上的空穴浓度P_(sh)都有重要影响,但其作用和方式是不同的。前一种取代主要是通过对空穴的复合和增强对空穴的局域化而使P_(sh)下降:后者则具有明显的退局域化作用,从而使得P_(sh)上升。当两种取代同时进行时,局域化作用不再是影响P_(sh)的因素,P_(sh)的增加来源于体系的总的空穴浓度的增加。还就超导电性与P_(sh)的关系作讨论。

The origin and the regularity of the variation of hole concentration as well as the crystal structure and superconducting critical temperature versus the doping contents of Co for Cu (I) and Ca for Y in YBa2Cu3O_y are studied in this paper. The results reveal that the pattern in which the hole concentration in Cu-O sheets, P_(sh), is influenced greatly by the substitution depends upon the different substituting elements as well as the different atomic sites, e.g. the decrease of P_(sh) in system substituted by Co for Cu (I) is from filling and localizing of holes, but the increase of P_(sh) in system of Ca replacing for Y is due to the delocalization effect of the holes. When Y and Cu (1) are substituted simutaneously with Ca and Co respectively, the generation instead of the localization effect cf the holes is important for the change of P_(sh). In addition, the relationship between P_(sh) and Fc is discussed.