Magnetometry with millimeter-scale anti-relaxation-coated alkali-metal   vapor cells
  Dynamic nonlinear magneto-optical-rotation signals with frequency- and amplitude-modulated laser light have been observed and investigated with a spherical glass cell of 3-mm diameter containing Cs metal with inner walls coated with paraffin. Intrinsic Zeeman relaxation rates of $\gamma/(2\pi)\approx 20 $Hz and lower have been observed. Favorable prospects of using millimeter-scale coated cells in portable magnetometers and secondary frequency references are discussed. 
M. V. Balabas, D. Budker, J. Kitching, P. D. D. Schwindt, and J. E.   Stalnaker