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arXiv · 2111.06587

Dimer Crystallization Induced by Elemental Substitution in the Honeycomb Lattice of Ru1-xOsxCl3

Kota Kataoka·Dirk Wulferding·Takeshi Yajima·Daisuke Nishio-Hamane·Daigorou Hirai·Seungyeol Lee·Kwang-Yong Choi·Zenji Hiroi
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Abstract

Substitution effects of Os for Ru in {\alpha}-RuCl3 are investigated in a wide composition range of 0 =< x =< 0.67 in Ru1-xOsxCl3 by X-ray and electron diffraction, magnetic susceptibility, heat capacity, and Raman spectroscopy measurements. Apart from the Kitaev physics with antiferromagnetic interactions increasing with x, a rich phase diagram is obtained, which includes an antiferromagnetic long-range order below 12 K for x =< 0.15, a dome-shaped spin-singlet dimer phase below 130 K for 0.15 =< x =< 0.40, and a magnetic short-range order for x > 0.40. A dimerization as similarly observed in {\alpha}-RuCl3 under high pressure occurs in the spin-singlet phase. It is suggested that Ru-Os pairs in the solid solutions tend to form dimers with short bonds and trigger the first-order transition in the presence of pseudo-threefold rotational symmetry for dimerization around a substituted Os atom only at low substitutions. This is a rare example of molecular orbital crystallization induced by elemental substitution in a highly disordered system. The short-range order at high substitutions may be related to a random-singlet state stabilized by bond disorder in the honeycomb net.

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Kota Kataoka, Dirk Wulferding, Takeshi Yajima, Daisuke Nishio-Hamane, Daigorou Hirai, Seungyeol Lee, Kwang-Yong Choi, Zenji Hiroi. 2021-11-12. Dimer Crystallization Induced by Elemental Substitution in the Honeycomb Lattice of Ru1-xOsxCl3. https://doi.org/10.7566/jpsj.91.014801

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