NMR Study of Antiferromagnet UPtGa5

We report spin–lattice relaxation time ( T 1 ) measurements at Ga and Pt sites in a single crystal sample of an itinerant antiferromagnet UPtGa 5 ( T N =27 K). In the paramagnetic state at high temperatures, the T -dependence of static susceptibility and 1/ T 1 T at Ga and Pt sites shows a similar behavior, indicating the dynamical susceptibility \textImχ( q ,ω) has no strong q -dependence at high temperatures. This behavior suggests a localized character of this compound at high temperatures. Around T N , 1/ T 1 T at Ga site increases rapidly due to critical slowing down behavior, in contrast a saturation behavior is observed at Pt site as the antiferromagnetic fluctuation cancels at Pt site. The characteristic spin fluctuation energy Γ is estimated using T 1 and previously obtained hyperfine parameters.