Anisotropic magnetic diffuse scattering in an easy-plane type antiferromagnet ErNi${}_2$Ge${}_2$

Abstract

We report on neutron scattering studies of a rare earth intermetallic compound ErNi${}_2$Ge${}_2$. Polarized neutron scattering experiments revealed that the magnetic ordered moment $\mathbf{m}$ lies in ab-plane. Taking account of a lack of the third higher harmonic reflection, ErNi${}_2$Ge${}_2$ is considered to have a helical magnetic structure. The magnetic scattering profiles along the $[100{]}^{\ast }$- and the $[110{]}^{\ast }$-directions are well described by the sum of Gaussian and modified-Lorentzian terms, even far below $T_N$, indicating that short-range orders coexist with a long-range order. Interestingly, the modified-Lorentzian-type diffuse scattering is not present in the profiles along the $[001{]}^{\ast }$-direction. The anisotropy of the diffuse scattering suggests that the short-range-order consists of one dimensional long-range helices along the c-axis.

4 pages, to be published in J. Phys.: Condens. Matter (HFM2008)