POLARIZATION OF THE SPIN-DENSITY WAVES IN LEAD

Experimental evidence that shows that lead has 12 small-amplitude spin-density waves (SDW's) with commensurate wave vectors Q(i) = {210} is reviewed. An unresolved question has been the polarization direction of the SDW's. Neutron-diffraction satellites from an s-band conduction-electron SDW occur only at +/- Q. The fractional modulation of each SDW is approximately 0.01, a value derived from the observed 10(5)-fold enhancement in the electronic specific heat at 0.5 K. Neutron-diffraction satellites at {210} will then have intensities approximately 3 X 10(-5) times that of a (nuclear) Bragg reflection provided the (linear) SDW's have transverse polarization. SDW satellite intensities will be zero if the SDW's are longitudinally polarized. Measurements using a highly filtered neutron beam at NIST's BT-9 spectrometer on a pure lead crystal at 4.2 K revealed no (210) satellite at the 5 X 10(-8) level. Consequently, one may conclude that the SDW's in lead are longitudinally polarized.