New Methods for NMR of Cuprate Superconductors

New nuclear magnetic resonance (NMR) methods for the investigation of high temperature superconductors are reported which alleviate many of the problems NMR faces in such materials. The methods rely on combining population transfers between quadrupolar split Zeeman levels with ordinary NMR experiments. Spins labeled in this manner can be investigated selectively, e.g., allowing the differentiation between isotopes, crystallographic sites, and misaligned grains. Examples for Cu NMR on ${\mathrm{YBa}}_2{\mathrm{Cu}}_4{\mathrm{O}}_8$ and ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_4$ are reported. The methods will also be applicable to other areas of solid state NMR.