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

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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.