Single-crystal neutron diffraction study of the magnetic structure of Er₃Co

The effect of the magnetic field applied along the main crystallographic directions on the magnetic structure of Er₃ Co has been studied by means of single-crystal neutron diffraction technique. At zero field the compound exhibits a noncoplanar commensurate magnetic structure with ferromagnetic alignment of the Er magnetic-moment projections along the b axis in an orthorhombic unit cell. The present measurements revealed that the application of the magnetic field along the c direction [c⊥ (ab)] leads to the pronounced metamagneticlike transition in the low-field region μ0 H<1.2 T, although, the magnetization curve does not exhibit any anomalies. Combining the present single-crystal diffraction and magnetization data with the results of the previous powder neutron diffraction study, we conclude that the nature of the magnetic ion, whether Kramers or non-Kramers, has a decisive effect on the commensurability of the magnetic structure of R₃ Co. In particular, the commensurate magnetic structure observed in Er₃ Co originate from the Kramers character of Er³⁺ ion in contrast to the incommensurate structures found earlier in R₃ Co with R= Tb and Ho.