Three-dimensional magnetism and the Dzyaloshinskii-Moriya interaction in <i>S</i> = 3/2 kagome staircase Co<sub>3</sub>V<sub>2</sub>O<sub>8</sub>.

Helton, Joel S; Butch, Nicholas P; Pajerowski, Daniel M; Barilo, Sergei N; Lynn, Jeffrey W · Sci Adv · 2020

basic_science · Level V

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Abstract

Time-of-flight neutron data reveal spin waves in the ferromagnetic ground state of the kagome staircase material Co<sub>3</sub>V<sub>2</sub>O<sub>8</sub>. While previous work has treated this material as quasi-two-dimensional, we find that an inherently three-dimensional description is needed to describe the spin wave spectrum throughout reciprocal space. Moreover, spin wave branches show gaps that point to an unexpectedly large Dzyaloshinskii-Moriya interaction on the nearest-neighbor bond, with <i>D</i> <sub>1</sub> ≥ <i>J</i> <sub>1</sub>/2. A better understanding of the Dzyaloshinskii-Moriya interaction in this material should shed light on the multiferroicity of the related Ni<sub>3</sub>V<sub>2</sub>O<sub>8</sub>. At a higher temperature where Co<sub>3</sub>V<sub>2</sub>O<sub>8</sub> displays an antiferromagnetic spin density wave structure, there are no well-defined spin wave excitations, with most of the spectral weight observed in broad diffuse scattering centered at the (0, 0.5, 0) antiferromagnetic Bragg peak.