Compass Correlations in a Square-Lattice Magnet

@misc{omar2026compass,
  title = {{Compass Correlations in a Square-Lattice Magnet}},
  author = {Otkur Omar and Matthias D. Frontzek and Gabriele Sala and Junying Shen and Xinmin Wang and Ze Hu and Zhuang Xu and Zecong Qin and Xin Tong and Joe Paddison and Max Hirschberger and Shinichiro Seki and Masaaki Matsuda and Matthew B. Stone and Andrew D. Christianson and Nguyen D. Khanh and Shang Gao},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.32157},
  eprint = {2610.32157},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.32157},
}

TY  - UNPB
TI  - Compass Correlations in a Square-Lattice Magnet
AU  - Otkur Omar
AU  - Matthias D. Frontzek
AU  - Gabriele Sala
AU  - Junying Shen
AU  - Xinmin Wang
AU  - Ze Hu
AU  - Zhuang Xu
AU  - Zecong Qin
AU  - Xin Tong
AU  - Joe Paddison
AU  - Max Hirschberger
AU  - Shinichiro Seki
AU  - Masaaki Matsuda
AU  - Matthew B. Stone
AU  - Andrew D. Christianson
AU  - Nguyen D. Khanh
AU  - Shang Gao
PY  - 2026
DA  - 2026/10/23
PB  - arXiv
DO  - 10.48550/arxiv.2610.32157
UR  - https://arxiv.org/abs/2610.32157
AB  - The square-lattice compass model is a paradigm of bond-dependent frustration, yet experimental evidence for its characteristic spin correlations has remained elusive. Here we identify compass correlations in the square-lattice intermetallic ErRu_2Si_2 using single-crystal neutron diffuse scattering. Comparative measurements on the isostructural compounds NdRu_2Si_2 and ErRu_2Si_2 reveal a pronounced contrast between nearly uniform diffuse rings in the former and strong intensity modulation between Brillouin zones in the latter. Through the magnetic neutron polarization factor, this modulation reveals compass correlations that couple moment orientation to the correlation wavevector. Crystal-field spectroscopy identifies four preferred in-plane orientations for the Er^3+ moments. A minimal compass-Heisenberg model incorporating this anisotropy quantitatively reproduces the diffuse scattering and accounts for the double-Q vortex-antivortex ground state. Fits with the compass couplings fixed at values set by the dipolar energy scale retain good agreement with the data, supporting a substantial dipolar contribution to the bond-dependent interactions. Our results establish a square-lattice platform for compass physics and suggest that dipolar interactions, acting together with local crystal-field anisotropy, can shape directional magnetic correlations alongside conduction-electron-mediated exchange.
ER  -