We have investigated the magnetic ground state of the antiferromagnetic Kondo-lattice compounds CeMAl$_{4}$Si$_{2}$ (M = Rh, Ir) using neutron powder diffraction. Although both of these compounds show two magnetic transitions $T_{N1}$ and $T_{N2}$ in
the bulk properties measurements, evidence for magnetic long-range order was only found below the lower transition $T_{N2}$. Analysis of the diffraction profiles reveals a commensurate antiferromagnetic structure with a propagation vector $mathbf{k}$= (0, 0, 1/2). The magnetic moment in the ordered state of CeRhAl$_{4}$Si$_{2}$ and CeIrAl$_{4}$Si$_{2}$ were determined to be 1.14(2) and 1.41(3) $mu_{B}$/Ce, respectively, and are parallel to the crystallographic $c$-axis in agreement with magnetic susceptibility measurements.
MnSi is a cubic compound with small magnetic anisotropy, which stabilizes a helimagnetic spin spiral that reduces to a ferromagnetic and antiferromagnetic state in the long- and short-wavelength limit, respectively. We report a comprehensive inelasti
c neutron scattering study of the collective magnetic excitations in the helimagnetic state of MnSi. In our study we observe a rich variety of seemingly anomalous excitation spectra, as measured in well over twenty different locations in reciprocal space. Using a model based on only three parameters, namely the measured pitch of the helix, the measured ferromagnetic spin wave stiffness and the amplitude of the signal, as the only free variable, we can simultaneously account for textit{all} of the measured spectra in excellent quantitative agreement with experiment. Our study identifies the formation of intense, strongly coupled bands of helimagnons as a universal characteristic of systems with weak chiral interactions.
