Linear magnetoelectric coupling without long-range magnetic order and rare-earth-free large magnetocaloric effect in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Co</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>8</mml:mn></mml:msub></mml:math>
Sampad Mukherjee, N. Mondal, Maurizio Polentarutti, Giorgio Bais, S. Majumdar, S. Giri
Abstract
The cobalt atoms within the crystal structure of ${\mathrm{Co}}_{3}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ arrange themselves into kagome staircase lattices. Our low-temperature synchrotron diffraction studies confirm a distortion in kagome lattices along the [010] direction associated with the anomalous thermal expansion of the unit cell volume below $\ensuremath{\sim}180$ K. At this temperature, a structural transition to a polar $Aba2$ space group from the high-temperature structure is suggested. This transition is further confirmed by Raman spectroscopy and is associated with the ferroelectric order at 180 K (${T}_{\mathrm{FE}}$). Below ${T}_{\mathrm{FE}}$, a significant linear magnetoelectric (ME) coupling is realized despite long-range magnetic order occurring below $\ensuremath{\sim}11$ K. Thus, ME coupling is linked to the distortion in the kagome lattice structure formed by the Co atoms. These correlations provide an opportunity for manipulating ME coupling at elevated temperatures. The compound exhibits a highly promising magnetocaloric effect in proximity to its magnetic order, constituting another appealing outcome. This characteristic is interesting for the exploration of rare-earth-free magnetocaloric materials.