An x-ray diffraction study reveals the valence-ordering structure in an intermediate-valence magnet YbPd with a CsCl structure. The valence of the Yb ions forms an incommensurate structure, characterized by the wave vector ($\pm$0.07 $\pm$0.07 1/2) below 130 K. At 105 K, the incommensurate structure turns into a commensurate structure, characterized by the wave vector (0 0 1/2). Based on the resonant x-ray diffraction spectra of the superlattice reflections, the valences of the Yb ions below 105 K are found to be 3$+$ and 2.6$+$. The origin of the long-wavelength modulation is discussed with the aid of an Ising model having next-nearest-neighbor interaction.

• Received 19 March 2013

DOI:https://doi.org/10.1103/PhysRevB.88.054109