NMR Studies of the magnetic order at low temperatures in the Antiferromagnetic Phase of Oxide High-T_c Superconductor

测量了掺氢四方YBa2Cu3O&lt；6X&gt；H_y粉末样品的反铁磁相(T_N=约410K)上Cu(1)和C(2)位的质子核磁共振和铜核磁共振谱.质子核磁共振研究发现，氢原子占据了缺氧层中铜(1)位附近.^1H核磁共振的谱线宽度DELTAomega在20K以下突然增加，T_2^&lt；-1&gt；和T_1^&lt；-1&gt；分别在20K和40K附近增强。在80K以下，核磁化强度不能以简单的指数方式恢复。在80K以下，控制T1的主要机制是空穴掺杂效应引起的磁场波动。这些增强和DELTAomega的突然增加归因于这种起伏的磁场。然而，在80K时，核磁化以简单的指数方式恢复。在80K以上，波动磁场对T_1的贡献迅速减小。在80K以上，其他T_1驰豫机制占主导地位。为了研究T_1，T_2，共振频率，以及在80K以上的高温区的T_1，T_2，共振频率和^&lt；63&gt；nqr的温度依赖关系，测量了Cu(2)位的CuNQR，研究了YBCO的反铁磁相。

Proton NMR and Cu NQR of Cu (1) and C (2) sites have been measured on the antiferromagnetic phase (T_N = ca.410 K) of a powdered sample of hydrogen-doped tetragonal YBa_2Cu_3O_<6+X>H_y. It was found by proton NMR studies that hydrogen atoms are occupied in the vicinity of Cu(1) site in the oxygen deficient layr. The line width, DELTAomega, of ^1H NMR increases abruptly below 20 K.The enhancements of T_2^<-1> and T_1^<-1> of ^<63>Cu (1) NQR occur around 20 K and 40 K,respectively. The nuclear magnetization does not recover in a simple exponential manner below 80 K.The predominant mechanism governing T_1 below 80 K was found to be the fluctuating magnetic fields induced by the hole doping effect. These enhancements and the abrupt increase in DELTAomega are attributed to this fluctuating magnetic field.Above 80 K,however, the nuclear magnetization recover in a simple exponential manner. The contribution of the fluctuating magnetic field to T_1 decreases rapidly above 80 K.Taking the place of the fluctuating field, other T_1 relaxation mechanismsm dominate above 80 K.In order to investigate the relaxation mechanism above 80 K,the temperature dependence of T_1, T_2, the resonance frequencies, and the line width of ^<63>NQR in the Cu (1) site has been measured in the high temperature region above 80 K.The measurement of Cu NQR in the Cu (2) site has also carried out to investigate the antiferromagnetic phase of YBCO.