NMR Study of a Heavy Fermion Compound YbAs

Nuclear magnetic resonance and relaxation studies on ⁷⁵As in an Yb-monopnictide YbAs have been carried out at temperatures down to 20mK to clarify the magnetic properties of this compound from a microscopic point of view. A notable result is that the spin-lattice relaxation rate 1/T₁ shows Fermi-liquid-like behavior given as (T₁T)^-1 = 2.9 (sK)^-1 below 0.2K. The constant value of (T₁T)^-1 in YbAs is discussed using the Korringa relation for a single impurity model to compare with those in other heavy Fermion compounds. The NMR spectra between 0.4 K and 0.6 K indicate that the paramagnetic and the antiferromagnetically ordered regions coexist. From these results, it is found that YbAs is a heavy Fermion compound which undergoes an antiferromagnetic transition.