Temperature dependence of nuclear spin shifts in cuprates

There exists by now an extended set of data on NMR spin shifts, $^k\! K_{\alpha,spin}$, measured for various nuclear species $k$ and directions $\alpha$ of the external field in a variety of cuprates. We present a phenomenological model that fits the temperature dependence $^k\! K_{\alpha,spin}(T)$ in the normal state of most of the published data in terms of a few parameters (including the pseudo gap) surprisingly well. The dependence of these parameter values on the compound and the doping level is presented and discussed. In particular, the pseudo gap temperature is compared to corresponding values deduced from the nuclear spin-lattice relaxation rates. Furthermore, we comment on the orbital shifts and their relationship to the measured values of $^k\! K_{\alpha,spin}$ at lowest temperatures.