Ca2CuWO6 develops antiferromagnetic order below 32 K, and a mean-field analysis identifies a single magnetic k-domain for the triclinic compound. The same comparison finds four degenerate k-domains for tetragonal Sr2CuWO6. The analysis relates that contrast to exchange-pathway splitting strongest within the Cu2 network.
How the pattern was identified
The study asks how structural complexity in Ca2CuWO6 relates to its magnetic ground state relative to Sr2CuWO6. The comparison places a triclinic compound beside a tetragonal one and uses a common supercell to put their magnetic patterns into a shared crystallographic frame. In that enlarged description, propagation vectors that look different in the original settings map onto the same supercell wave vector.
Researchers synthesized approximately 2 g of polycrystalline Ca2CuWO6 powder. They measured DC susceptibility with SQUID magnetometry and collected time-of-flight neutron powder diffraction, then used FullProf Rietveld refinement to analyze the crystal and magnetic structures. The separate mean-field analysis used a Heisenberg interaction model and evaluated exchange-matrix eigenvalues across the first Brillouin zone, the basic repeating region used to compare magnetic patterns.
When the powder was cooled to 1.5 K, additional Bragg intensities appeared below T_N = 32 K. An anomalous DC susceptibility signal at the same transition supported a magnetic origin for those features. A search across possible magnetic wave vectors indexed them with k = (1/2, 1/2, 0).
A collinear order
Rietveld refinement supported a collinear arrangement of the copper moments. The inequivalent Cu1 and Cu2 sites carried moments of equal magnitude but opposite direction, with an ordered moment of 0.66(3) μB per Cu at 1.5 K. Collinear here means the moments share one line while alternating direction.
As the sample cooled through the transition, the ordered moment grew continuously below T_N and was essentially saturated below about 10 K. A four-parameter fit gave a low-temperature moment m0 = 0.67(2) μB/Cu and T_N = 32(5) K. The two shape parameters, α ∼ 2.5 and β ∼ 0.24, were strongly linked in the fit; the authors said β was not a critical exponent.
One motif, different routes
The comparison points to a shared magnetic motif. After the structures were placed in a common supercell, the study reported a magnetic arrangement with tungsten-mediated, second-neighbor interactions. In practical terms, the apparently different propagation vectors can describe the same repeating magnetic pattern once the two crystallographic settings are expressed in that common cell.
The routes by which those interactions are represented are not identical. In the tetragonal Sr2CuWO6 model, the exchange map contains one nearest-neighbor exchange, J1, and one next-nearest-neighbor exchange, J2. In triclinic Ca2CuWO6, the next-neighbor topology is represented by four strong exchanges within two Cu-orbit networks.
Why the domain result remains tentative
Mean-field calculations gave two Cu-orbit modes for Ca2CuWO6, with exchange-matrix eigenvalues of −18.10 and −22.42 meV. The lower-energy mode was weighted toward the Cu2 network, and the reported calculation gave Δk = 0. The same analysis reported one Ca k-domain, versus four degenerate domains for Sr2CuWO6.
The domain-selection explanation remains model-dependent. Weak J3 differences were not quantitatively resolved. The neutron powder data directly support the low-temperature Ca magnetic structure and ordered moment, while the shared-motif and domain conclusions come from the common-supercell and mean-field comparisons.
The result is therefore a material-specific comparison, not evidence on its own for a general rule about how lower symmetry selects magnetic domains. The supplied document is an arXiv preprint, version 1, dated 26 August 2026.
Paper data and sources
Original title: Quasi two dimensional magnetic structure of the triclinic double perovskite Ca$_2$CuWO$_6$
Authors: Bangye Qin, Dmitry D. Khalyavin, Xuan Liang et al.
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-26
DOI: Not available
Original paper · Full text