^<141>Pr nuclear spin relaxation time in Pr and related compounds.

稀土自旋回波核磁共振测量了Pr化合物及其相关化合物：RCo_<5+x> (R=Pr, Tb), Pr_2Fe_<14>B,Pr_xGd_<1-x>Ni, Sm_xGd_<1-x>Ni和RFe_<11>Ti （R=稀土）。Pr_xGd_<1-x>Ni的^<141>Pr核磁共振信号出现在较宽的频率范围内。在Pr_<0.2>Gd_<0.8>Ni的情况下，频谱宽度约为1000MHz，在2800 ~ 3800MHz的频率范围内，与Pr_2Fe_<14>B和Sm_xGd_<1-x>Ni不同。超精细场分析结果表明，PrCo_5和Pr_<0.2>Gd_<0.8>Ni的稀土离子磁矩分别为2.4和2.6mu_B。在1.4K ~ 4.2K的温度范围内，在PrCo_5、Pr_2Fe_<14>B和Pr_xGd_<1-x>Ni上测量了原子核自旋弛豫时间T_2。发现自旋-自旋弛豫服从简单的指数函数，呈现快速衰减。在PrCo_5中，1.4K时T_2为4.2musec， 4.2K时T_2为2.1musec。在Pr_xGd_<1-x>中，当x=0.2和0.35时，T_2在1.4K时分别为-5musec和-3musec。在Sm_<0.2>Gd_<0.8>Ni中，它们大约是^<147>Sm的1/20到1/30。假设观测到的信号主要来自于-1/2 <互变异构体> 1/2跃迁对应的线，则利用关系T_1/T_2= (I+1/2)^2估计自旋晶格弛豫时间T_1。得到PrCo_5和Pr_xGd_<1-x>Ni的T_1T分别为- 110kmusc和- 50kmusc。对于Pr_2Fe_<14>B， f和g位点的T_1T分别为900kmusc和300kmusc。

Rare-earth spin-echo NMR measurements have been carried out on Pr compounds and the related compounds : RCo_<5+x> (R=Pr, Tb), Pr_2Fe_<14>B,Pr_xGd_<1-x>Ni, Sm_xGd_<1-x>Ni and RFe_<11>Ti (R=rare-earth). The ^<141>Pr NMR signal of Pr_xGd_<1-x>Ni appeared in the wide frequency range. In the case of Pr_<0.2>Gd_<0.8>Ni, the width of spectrum was about 1000MHz, in the frequency range from 2800 to 3800MHz, which was different from those of Pr_2Fe_<14>B and Sm_xGd_<1-x>Ni. The magnetic moments of rare-earth ions in the compounds which were estimated from the hyperfine field analysis were 2.4 and 2.6mu_B for PrCo_5 and Pr_<0.2>Gd_<0.8>Ni, respectively. ^<141>Pr nuclear spin-spin relaxation times, T_2, have been measured on PrCo_5, Pr_2Fe_<14>B and Pr_xGd_<1-x>Ni in the temperature range from 1.4K to 4.2K.It was found that the spin-spin relaxation followed a simple exponential function and showed fast decay. In PrCo_5, T_2 were 4.2musec at 1.4K and 2.1musec at 4.2K.In Pr_xGd_<1-x>Ni, T_2 at 1.4K were -5musec and -3musec for x=0.2 and 0.35, respectively. These were roughly 1/20 to 1/30 of ^<147>Sm in Sm_<0.2>Gd_<0.8>Ni. Assuming that the observed signals arised mostly from the line corresponding to the -1/2 <tautomer> 1/2 transition, the spin-lattice relaxation time, T_1, was estimated by using the relation T_1/T_2= (I+1/2)^2. T_1T was obtained to be - 110Kmusec and -50Kmusec for PrCo_5 and Pr_xGd_<1-x>Ni, respectively. For Pr_2Fe_<14>B, T_1T were obtained to be 900Kmusec and 300Kmusec for the f and g sites, respectively.