Magnetic ordering in the XY pyrochlore antiferromagnet Er2Ti2O7:: a spherical neutron polarimetry study

Er2Ti2O7 has been proposed as a realization of the XY 111 pyrochlore antiferromagnet with dipolar interactions, where the spins of Er3+ lie perpendicular to the 111 local axes. Below a Neel temperature of T-N = 1.173 K magnetic order with the propagation vector k = (000) occurs. Previous powder neutron diffraction studies were not able to determine details of the magnetic ordering beyond its symmetry due to powder averaging. In an attempt to resolve the questions as regards the ordering in this model magnet we performed a spherical neutron polarimetry experiment using CRYOPAD. The analysis of these data and a proposed magnetic order are presented.