• He, Z.
• Jellyman, E.
• Birk, J. O.
• Blackburn, E.
• Zaharko, O.
• Shen, L.

Abstract

<jats:title>Abstract</jats:title><jats:p>We explore magnetic order in the quantum spin chain compound SrCo<jats:sub>2</jats:sub>V<jats:sub>2</jats:sub>O<jats:sub>8</jats:sub> up to 14.9 T and down to 50 mK, using single-crystal neutron diffraction. Upon cooling in zero-field, commensurate antiferromagnetic (C-AFM) order with modulation vector <jats:inline-formula><jats:tex-math> <?CDATA ${{{k}}}_{{{C}}}$?> </jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msub><mml:mrow><mml:mi mathvariant="bold-italic">k</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:msub></mml:math><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="njpab2b7aieqn1.gif" xlink:type="simple" /></jats:inline-formula> = (0, 0, 1) develops below <jats:italic>T</jats:italic><jats:sub>N</jats:sub> ≃ 5.0 K. Applying an external magnetic field (<jats:italic>H</jats:italic>∥<jats:italic>c</jats:italic> axis) destabilizes this C-AFM order, leading to an order-disorder transition between <jats:italic>T</jats:italic><jats:sub>N</jats:sub> and ∼1.5 K. Below 1.5 K, a commensurate to incommensurate (IC-AFM) transition occurs at 3.9 T, above which the magnetic reflections can be indexed by <jats:inline-formula><jats:tex-math> <?CDATA ${{{k}}}_{{{IC}}}$?> </jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msub><mml:mrow><mml:mi mathvariant="bold-italic">k</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">IC</mml:mi></mml:mrow></mml:msub></mml:math><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="njpab2b7aieqn2.gif" xlink:type="simple" /></jats:inline-formula> = (0, 0, 1 ± <jats:italic>δl</jats:italic>). The incommensurability <jats:italic>δl</jats:italic> scales monotonically with <jats:italic>H</jats:italic> until the IC-AFM order disappears around 7.0 T. Magnetic reflections modulated by <jats:inline-formula><jats:tex-math> <?CDATA ${{{k}}}_{{{C}}}$?> </jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msub><mml:mrow><mml:mi mathvariant="bold-italic">k</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:msub></mml:math><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="njpab2b7aieqn3.gif" xlink:type="simple" /></jats:inline-formula> emerge again at higher fields. While the characters of the C-AFM, IC-AFM and the emergent AFM order in SrCo<jats:sub>2</jats:sub>V<jats:sub>2</jats:sub>O<jats:sub>8</jats:sub> appear to fit the descriptions of the Néel, longitudinal spin density wave and transverse AFM order observed in the related compound BaCo<jats:sub>2</jats:sub>V<jats:sub>2</jats:sub>O<jats:sub>8</jats:sub>, our results also reveal several unique signatures that are not present in the latter, highlighting the inadequacy of mean-field theory in addressing the complex magnetic order in systems of this class.</jats:p>

Topics

• density
• compound
• phase
• theory
• atomic force microscopy
• neutron diffraction
• phase diagram
• ion chromatography