SPHERICAL NEUTRON POLARIMETRY STUDY OF THE ZERO-FIELD MAGNETIC STRUCTURES OF NEODYMIUM USING CRYOPAD II

Abstract Due to their complex nature, an investigation of the zero-field magnetic structures of Nd has been started using CRYOPAD, the ILL zero-field neutron polarimeter available on IN20. Having set the incident polarisation to any desired direction, CRYOPAD then analyses the magnitude and direction of the polarisation vector of the scattered beam to a precision of 3° at a given momentum transfer. We have confirmed that the moments in the 2- q phase, which order solely on the hexagonal sites of the DHCP structure, are confined to the basal plane at 11.2 K. This was also found to be the case for the moments at the hexagonal sites at 7.6 K in the 3- q phase. Below 8.3 K, the moments on the cubic sites become ordered and we observe both a c -axis and basal plane component. We observe for the first time that the angle between these moments and the basal plane increases continuously with cooling through the 3- q phase.