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

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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.