Sensitive and Non-destractive Concentration Analysis of Oxygen in High T_c Superconductor by Muonic X-ray

为了研究铜氧化物La_<1-chi>Sr_<chi>CuO_<4-delta>的超导性质与氧浓度的关系，我们对chi =0.1, 0.14和0.15的单晶样品进行了一系列的介子x射线测量，负介子自旋旋转测量和SQUID测量。氧浓度的无损和高灵敏度测量是这类研究中最具挑战性的课题之一。为了突破这种情况，我们应用了元素成分分析方法，使用了经过多次改进的μ x射线，以达到所需的灵敏度，即氧浓度标称值的0.1%数量级。对于La_<1-chi>Sr_<chi>CuO_<4-delta>及其母化合物CuO、La_2O_3和SrCO_3，在KEK-MSL、TRIUMF和RIKEN/RAL进行了四年的子x射线测量。最后，我们在133 keV的声子氧x射线强度测量中获得了15的信噪比，比常规测量高了近一个数量级。在提高分辨率的过程中，当S/N比为5时，我们在(a)2 kbarr和(b)1 barr的环境氧气中退火，测量了chi=0.14的单晶样品中氧浓度的变化：首次在块状材料中检测到氧浓度下降了标称值的0.6(0.5)%。在信噪比为15的改进实验中，浓度测量的实验误差预计为现值的1/5。在（muO）SR实验中，我们成功地分别观察了顶端氧和平面氧附近导电电子的行为。对氧浓度依赖性的系统研究正在进行中。

In order to study the oxygen concentration dependencies of superconducting properties of cuprate oxides La_<1-chi>Sr_<chi>CuO_<4-delta>, we have performed a series of muonic X-ray measurements, negative muon spin rotaion measurements and SQUID measurements for the well defined single crystalline samples of chi =0.1, 0.14 and 0.15.Non-destructive and high-sensitive measurement of oxygen concentration is one of the most challenging subjects in such a. study. To break through the situation, we have applied the elemental composition analysis method by using muonic X-rays with several improvements to achieve the required sensitivity of the order of 0.1% of the nominal value in oxygen concentration.For La_<1-chi>Sr_<chi>CuO_<4-delta> and mother compounds CuO, La_2O_3, and SrCO_3, the muonic X-ray measurements have been performed in KEK-MSL, TRIUMF and RIKEN/RAL over four years. Finally, we have attained the S/N ratio of 15 in the intensity measurement of muonic oxygen X-ray at 133 keV which is almost an order higher than in the conventional measurements. In the process of the improvement of the resolution when S/N ratio was 5, we have measured the change of oxygen concentration in the single crystalline sample with chi=0.14 by annealing in ambient oxygen gas with pressure of(a)2 kbarr and(b)1 barr : a decrease of oxygen concentration by 0.6(0.5)% of the nominal value was detected in the bulk material for the first time. Experimental error in the concentration measurements is expectedto be 1/5 of the present value in the improved experiments with S/N ratio of 15. In the (muO)SR experiments, we have succeed to observe the behavior of the conductinelectrons in the vicinities of apical oxygens and plane oxygens separately. The systematic study of oxygen concentration dependencies is in progress.