Spin dynamics of the field-induced spin density wave phases in (TMTSF)$_2$ClO$_4$ in tilted magnetic fields*

The spin dynamics of the different subphases of the field-induced spin density wave (FISDW) ground state in (TMTSF)$_2$ClO$_4$ was investigated using simultaneous $^{77}$Se nuclear magnetic resonance (NMR) and electrical transport. The metallic and FISDW phases were accessed by rotating the sample along its most conducting axis in a constant magnetic field H and constant temperature. At a fixed field of 30 T and constant temperature 1.47K, we report observation of divergence in the spin-lattice relaxation rate 1/T$_1$ at angles corresponding to H$_{\perp}$=H$\cos(\theta)$ $\sim$ 6.4T, 15.9T, and 26T FISDW phase transitions. There is a gradual increase in 1/T$_1$ in the 2nd-order/FISDW cascade region and a nearly metallic-like behavior deep in the final$\backslash$reentrant SDW phase is observed. RF enhancements in the metallic and FISDW phases were also measured. The details will be discussed.