NMR Spin-Lattice Relaxation and EPR Linewidth in High Tc Materials
The nuclear-magnetic-resonance (NMR) spin-lattice relaxation rate (1/T1) and electron-paramagnetic-resonance (EPR) linewidth (T1) are calculated for La2CuO4 in both the paramagnetic and antiferromagnetic regimes. The NMR T1 at first shortens with increasing temperature in the antiferromagnetic regime, then in the vicinity of TN lengthens as (ξ/a)-1, where ξ is the two-dimensional spin-correlation length and a is the lattice constant, and then shortens above T ~ J/2, where J is the in-plane exchange coupling and then to saturate at T>J. The large broadening of the EPR at room temperature is shown to narrow with increasing temperature as (ξ/a)3, becoming observable in principal at T > 800 K. A scaling proposal is put forward for application of these results to conducting cuprates.
PACS numbers75.10.Jm 74.70Vy 74.30.Gn
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