Er2Ti2O7 has been proposed as a realization of the pyrochlore antiferromagnet with dipolar interactions, where the spins of Er3+ lie perpendicular to the local axes. Below a Néel temperature of TN = 1.173 K magnetic order with the propagation vector 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.

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The magnetization distribution due to the Cr3+ ion in Cr2O3 has been determined using spherical neutron polarimetry. The magnetic structure factors of h 0 l reflections have been measured out to sin θ/λ = 0.75 Å-1. The results show that the Cr3+ magnetic moment is reduced by the zero-point spin deviation and by covalent mixing to 2.48 µB. They are consistent with the Cr d electrons being in the trigonally symmetric a1 and e orbitals derived from the cubic orbitals with t2g symmetry. There is a small but significant magnetization which is not accounted for by these orbitals, which is attributed to covalent overlap. Its symmetry is consistent with the magneto-electric susceptibility.

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The magnetic ground-state of copper metaborate CuB 2 O 4 was investigated with unpolarized and polarized neutron scattering. A phase transition was found at T N ϭ21 K to a commensurate weakly ferromagnetic state followed by a second transition at T*ϭ10 K to an incommensurate magnetic structure. Neutron diffraction revealed a continuously changing magnetic propagation vector below T*, and unusually asymmetric magnetic satellite reflections. Additionally, diffuse scattering is observed in the temperature range 1.5 KрTр30 K. The magnetic structure determined in both phases are shown to be consistent with results of symmetry analysis. In particular, we find that only one of the two inequivalent Cu 2ϩ sublattice fully orders down to the lowest temperature. Our results show that the complex magnetic behavior of copper metaborate is a consequence of mutual interaction between the two Cu 2ϩ sublattices with different ordering temperatures.

We present a comprehensive analysis of high-resolution neutron scattering data involving neutron spin echo spectroscopy and spherical polarimetry, which confirm the first-order nature of the helical transition in MnSi. The experiments reveal the existence of a totally chiral dynamic phase in a very narrow temperature range above T C . This unconventional magnetic short-range order has a topology similar to that of a skyrmion liquid or the blue phases of liquid crystals.

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