Zeeman splitting and nonlinear field-dependence in superfluid 3He
  We have studied the acoustic Faraday effect in superfluid 3He up to significantly larger magnetic fields than in previous experiments achieving rotations of the polarization of transverse sound as large as 1710^{\circ}. We report nonlinear field effects, and use the linear results to determine the Zeeman splitting of the imaginary squashing mode (ISQ) frequency in 3He-B. 
C. A. Collett, J. Pollanen, J. I. A. Li, W. J. Gannon, W. P. Halperin
cond-mat.other cond-mat.supr-con