Magnetic structures described by multiple magnetic modulation wave vectors (q-vectors) have attracted great interest in condensed matter physics, since the discovery of magnetic skyrmion lattices in the chiral magnet MnSi[1]. By applying a magnetic field just below the magnetic ordering temperature, MnSi exhibits a triangular lattice of swirling spin objects, namely the triangular skyrmion lattice, on a plane perpendicular to the applied field. This spin texture is described by superposing three screw-type magnetic modulations and  a uniform magnetization component, and thus referred to as multiple-q magnetic order. 

Although the multiple-q states are often investigated by x-ray or neutron scattering experiments, it is not straightforward to distinguish them from the multi-domain states of single-q magnetic orders. In the present study, we investigate magnetic orders of the intermetallic compound CeRh₂Si₂ under the application of uniaxial stress to address this issue. This system has a centrosymmetric tetragonal crystal structure (space group:  I4/mmm)[2]. A previous study revealed that CeRh₂Si₂  exhibits two magnetically ordered phases in zero magnetic field[3],  and suggested that the low temperature phase is a multiple-q phase[4].

In order to verify the multiple-q nature of the ground state of CeRh₂Si₂, we applied uniaxial stress to single crystal samples and performed neutron scattering, magnetization, and resistivity measurements.   We observed remarkable anisotropy in magnetization,   resistivity, and neutron diffraction intensities under uniaxial stress only in the high-temperature magnetic phase, indicating that there are irreversible changes in volume fraction of single-q magnetic domains. By contrast, the ground state shows a robust stability against the uniaxial stress arising from the fourfold rotational symmetry of the multiple-q order. The results indicates that the application of the (relatively weak) uniaxial could be a useful tool to distinguish multiple-q orders from single-q orders. 

[1] S. Mühlbauer, B. Binz, F. Jonietz, C. Pfleiderer, A. Rosch, A.Neubauer, R.Georgii, and P.Böni, Science 323, 915 (2009).
[2] C. Godart, L. Gupta, and M. Ravet-Krill, Journal of the Less Common Metals 94, 187 (1983).
[3] B. H. Grier, J. M. Lawrence, V. Murgai, and R. D. Parks, Physical Review B 29, 2664 (1984).
[4] S. Kawarazaki, M. Sato, Y. Miyako, N. Chigusa, K. Watanabe, N. Metoki, Y. Koike, and M. Nishi, Physical Review B, 61, 4167 (1999).