Analytical method to correct the neutron polarisation for triple-axis data

Polarised neutron scattering is the method of choice to study magnetism in condensed matter. Polarised neutrons are yet typically very low in flux and complex experimental configurations further reduce the count rate, neutron polarisation corrections would therefore be needed. Here we analytically derive formulae of the corrected partial differential scattering cross sections. The analytical method is designed for the longitudinal polarisation analysis, and the correction generally holds for time-independent polarised neutrons with a triple-axis spectrometer. We then applied the correction to recent results of our $P_x$ experiment on Y$_3$Fe$_5$O$_{12}$. Although there is a difficulty with experimental determination of inefficiency parameters of neutron spin polarisers and flippers, the correction appears to work properly.Comment: 6 pages, 2 figure

Successive phase transitions and phase diagrams of the quasi-two-dimensional triangular antiferromagnet Rb4Mn(MoO4)3

Comprehensive experimental studies by magnetic, thermal and neutron measurements have clarified that Rb4Mn(MoO4)3 is a model system of a quasi-2D triangular Heisenberg antiferromagnet with an easy-axis anisotropy, exhibiting successive transitions across an intermediate collinear phase. As a rare case for geometrically frustrated magnetism, quantitative agreement between experiment and theory is found for complete, anisotropic phase diagrams as well as magnetic properties.Comment: 4 pages, 5 figure

Ferro-quadrupolar ordering in PrTi2_2Al20_{20}

Origin of the non-magnetic phase transition in PrTi$_2$Al$_{20}$, reported earlier in the macroscopic study, has been asserted microscopically using elastic and inelastic neutron scattering techniques. It has been shown spectroscopically that the crystalline-electric-field ground state is a non-magnetic $\Gamma_3$ doublet, whereas the excited states are two triplets ($\Gamma_4$ and $\Gamma_5$) and a singlet ($\Gamma_1$). The diffraction experiment under external magnetic field shows that the non-magnetic transition is indeed ferro-quadrupolar ordering, which takes place as a consequence of cooperative removal of the ground-state-doublet degeneracy. It is therefore concluded that PrTi$_2$Al$_{20}$ is another rare example of Pr compounds exhibiting non-magnetic quadrupolar order.Comment: 7pages, 7 figure, and 1 table, submitted to PR