Metamagnetic texture in a polar antiferromagnet


The notion of a simple ordered state implies homogeneity. If the order is established by a broken symmetry, the elementary Landau theory of phase transitions shows that only one symmetry mode describes this state. At the exact points of phase coexistence, domain states composed of large regions of different phases can be stabilized by long-range interactions. In uniaxial antiferromagnets, so-called metamagnetism is an example of such behaviour where antiferromagnetic and field-induced, spin-polarized paramagnetic/ferromagnetic states coexist at a jump-like transition in the magnetic phase diagram. Here, by combining experiments with theoretical analysis, we show that a different type of mixed state between antiferromagnetism and ferromagnetism can be created in certain non-centrosymmetric materials. In small-angle neutron scattering experiments, we observe a field-driven spin state in the layered antiferromagnet Ca3Ru2O7, which is modulated on a scale between 8 and 20 nm and has both antiferromagnetic and ferromagnetic parts. We call this state a metamagnetic texture and attribute its appearance to the chiral twisting effects of the asymmetric Dzyaloshinskii–Moriya exchange. The observation can be understood as an extraordinary coexistence—in one thermodynamic state—of spin orders that belong to different symmetries. The complex nature of this metamagnetic state is demonstrated experimentally by measurements of anomalies in electronic transport that reflect the spin polarization in the metamagnetic texture; determination of the magnetic orbital moments, which support the existence of strong spin–orbit effects, is a pre-requisite for the mechanism of twisted magnetic states in this material. Our findings provide an example of a rich and largely unexplored class of textured states. Such textures mediate between different ordering modes near phase coexistence, and produce extremely rich phase diagrams.

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Fig. 1: Bulk properties of Ca3Ru2O7 measured with the magnetic field along the b axis on the same single crystal.
Fig. 2: SANS patterns.
Fig. 3: Metamagnetic textures in Ca3Ru2O7.
Fig. 4: Schematics of metamagnetic texture in Ca3Ru2O7 and temperature-field phase diagrams.

Data availability

The data that support the plots within this paper can be downloaded at The datasets for the SANS experiments on D33 are available from the Institute Laue–Langevin data portal (


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We thank U. Nitzsche for technical support with FPLO. N.K. acknowledges the support from JSPS KAKENHI (nos JP17H06136 and JP18K04715) and JST-Mirai Program (no. JPMJMI18A3) in Japan. D.A.S. thanks C. Geibel for the critical reading of the manuscript and constructive comments. Access to NG7 SANS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under agreement no. DMR-1508249. We thank J. Krzywon and Y. Qiang for technical support during the SANS experiment at NIST. This work is partly based on experiments performed at the Swiss spallation neutron source SINQ, Paul Scherrer Institute, Villigen, Switzerland. Certain commercial equipment, instruments, or materials are identified in this article to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.

Author information

U.K.R. conceived the project. U.K.R., A.P.M. and D.A.S. supervised the project. N.K. and D.A.S. grew single crystals. D.A.S oriented and characterized samples. H.B. and U.B. analysed the crystal structure. T.H. performed the electrical transport measurements and analysed the Hall effect data. K.K. performed XMCD measurements. D.A.S., R.C., J.S.W. and M.B. performed SANS measurements. D.A.S. and E.R. carried out neutron diffraction experiments. U.K.R. carried out density functional theory calculations and developed the Landau–Ginzburg-type free-energy theory. D.A.S. and U.K.R wrote the manuscript with contributions from all co-authors.

Correspondence to D. A. Sokolov.

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