Unique magnetic structure of YbCo${}_2$Si${}_2$

Abstract

We report on the results of powder and single crystal neutron diffraction to investigate the magnetic order in YbCo${}_2$Si${}_2$ below the Néel temperature $T_{\mathrm{N}}=1.7$K in detail. Two different magnetically ordered phases can clearly be distinguished. At lowest temperatures a commensurate magnetic structure with a propagation vector ${\mathbf{k}}_1=(0.250.251)$ is found, while the intermediate phase ($T>0.9$K) is characterized by an incommensurate magnetic structure with ${\mathbf{k}}_2=(0.250.0861)$. The magnetic structure in YbCo${}_2$Si${}_2$ is in marked contrast to all other known RCo${}_2$Si${}_2$ compounds (R = rare earth element) likely due to some itineracy of the Yb 4f states being responsible for the magnetism.

9 pages, 7 figures, accepted for publication in Phys. Rev. B