Magnetic moment directions in the 3-q phase of neodymium from neutron polarimetry with CRYOPAD

CRYOPAD has been used to study the moment directions in the zero held magne tic structures of the rare-earth metal neodymium. Results taken in the 3-q phase between approximate to 6 K and approximate to 8 K are presented. Here the directions of the moments giving rise to the modulation wave vectors q (1) and q(2) (relating primarily to the moments on the hexagonal sites of t he DHCP nuclear structure) stay close to a* as one traverses the phase. Thi s is not the case for the moment giving rise to the third modulation wave v ector q(3) (relating primarily to the moments on the cubic sites). At the h igh-temperature end of the 3-q phase this moment is in the a*-c* plane almo st parallel to a*, but with a large c* axis component developing as the tem perature is reduced. q(3) is split along c by tau = 0.052 tau(001) near 8 K . The tau(+) satellite is due to a moment in the a*-c* plane with a positiv e c* axis component whereas the tau - satellite is due to a moment in the a *-c* plane with a negative c* axis component equal in magnitude to that of tau(+). This result could not have been obtained without being able to meas ure the transverse component of polarisation. (C) 1999 Elsevier Science B.V . All rights reserved.