Antiferromagnetism and Superconductivity in Zn-doped YBCO

在本研究期间获得的主要结果是以下内容：1. We have carried out measurements of the magnetic excitation spectra（-） in single crystals of Yba-D22-D23-D26+y-D2 （YBCO-D26 +y-D2）（y ~ 0.4 and 0.45）。在295“K.K.， the χ”-两个样本的ω曲线在低能量区域都很轻微地捕捉，有人认为即使在房间温度下也存在单一相关性。我们可以将singlet formation persists far above the so-called spin gap temperature的fluctation of the singlet formation perature（~ 150？）， possibly to fiby D20 ye D2 at around which various transport anomalies set in （for example Hall coefficients），并且that the singlet correlation and the antiferromaginetic correlation begin to developp almost simultaneously. 2. Recently， it has been reported that in the magnetic excitation spectra of a 0. 5% Zn-doped YBCO D27 y D2 sample， a sharp peak （resonance peak） can be observed at （\，\） even far above锯齿D2c y D2。结果更类似于在未掺杂的YBCO样本中观察到的结果，建议在最理想的掺杂系统中显著地增强单个相关性（或假间隙）。In order to see this possibly， we have measured various quantities which are sensitive to the existence of the singlet pairs， the BイイD22 uイエD2 phonon， NMR relaxation rate and the in-plane resistence of YB针织D2 a2针织D2（CuイD21-x针织D2 Zn针织D2）针织D2 O针织D27针织D2（x ~ 0.005）。这些数量并不显示这类反常的依赖性，即在未掺杂的YBCO样本中观察到，或者没有证据表明锌掺杂已经发现的假间隙上的增强。然后，由于对磁性激发特性上的锌掺杂效应的完整理解，它似乎有必要研究其确定的动力-能量空间结构由共振-峰值组件组成，位于（π，π）和另一个组成部分，其中一个在inbommensurate q-point上达到峰值。

Main results obtained in this research period are the followings.1. We have carried out measurements of the magnetic excitation spectra χ"(ω) in single crystals of Yba ィイD22ィエD2CuィイD23ィエD2OィイD26+yィエD2 (YBCOィイD26+yィエD2)(y〜0.4 and 0.45). At 295Κ, the χ"-ω curves of both samples are slightly concave in the low energy region, which suggest that the singlet correlation exists even at room temperature. We can conclude that the fluctation of the singlet formation persists far above the so-called spin gap temperature ΤィイD2SGィエD2 (〜150Κ), possibly to ΤィイD20ィエD2 at around which various transport anomalies set in (for example Hall coefficients), and that the singlet correlation and the antiferromaginetic correlation begin to develop almost simultaneously.2. Recently, it has been reported that in the magnetic excitation spectra of a 0.5% Zn-doped YBCOィイD27ィエD2 sample, a sharp peak (resonance peak) can be observed at (π, π) even far above ΤィイD2cィエD2. The results is rather similar to that observed in underdoped YBCO samples, suggesting that the doping significantly enhance the singlet correlation (or the pseudo gap) even in the optimally doped system. In order to see this possibly, we have measured various quantities which are sensitive to the existence of the singlet pairs, the BィイD22uィエD2 phonon, NMR relaxation rate and the in-plane resistivity of YBΤィイD2a2ィエD2(CuィイD21-xィエD2ZnィイD2xィエD2)ィイD23ィエD2OィイD27ィエD2(x〜0.005). These quantities do not exhibit such the anomalous Τ-dependence as observed in underdoped YBCO samples, or no evidence for the enhancement on the pseudo gap by the Zn doping has been found. Then, for the complete understanding of the Zn-doping effects on the magnetic excitation spectra, it seems to be necessary to study its detailed momentum-energy space structure composed of the resonance-peak component centered at (π, π) and another component which has peak at the inbommensurate q-point.