Diagnosis of quantum criticality by nuclear spin-echo decay method

The Gaussian spin–spin relaxation time T2G, as determined by nuclear magnetic resonance (NMR) spin-echo decay measurements, is found to be useful for diagnosis of quantum critical behaviour in heavy-fermion systems. Combining T2G with the spin–lattice relaxation time T1, the exponent f of the quantity T1T=T 2 2G T is predicted to be sensitive to the type of quantum criticality in the system concerned. In fact, in the heavy-fermion system USn3 near the quantum critical point, T1T=T 2 2G is found to be constant, as expected for a 3D-SDW magnetic instability.