Magnetic correlations in ${\mathrm{YBaCo}}_{4}{\mathrm{O}}_{7}$ on kagome and triangular lattices

Magnetic correlations in ${YBaCo}_{4} O_{7}$ on kagome and triangular lattices

Minoru Soda, Shinichi Itoh, Tetsuya Yokoo, Georg Ehlers, Hazuki Kawano-Furukawa, and Takatsugu Masuda

Phys. Rev. B 101, 214444 – Published 29 June 2020

Abstract

Magnetic correlation in ${YBaCo}_{4} O_{7}$ with kagome and triangular lattices was studied through inelastic-neutron-scattering measurements on a single crystal sample. The broad magnetic excitation was observed below 45 meV and showed dispersions both within the $c$ plane and along the $c$ axis. The wave vector with the minimum energy of the magnetic excitation was totally different from the magnetic Bragg point. Our analysis with the first-moment-sum rule suggests that Co ions in ${YBaCo}_{4} O_{7}$ form a unique three-dimensional network with the geometrically frustration.

Received 12 March 2020
Revised 13 May 2020
Accepted 17 June 2020

DOI:https://doi.org/10.1103/PhysRevB.101.214444

Physics Subject Headings (PhySH)

Frustrated magnetism

Pyrochlores

Inelastic neutron scattering Neutron scattering

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Minoru Soda ^1,2,3, Shinichi Itoh⁴, Tetsuya Yokoo⁴, Georg Ehlers⁵, Hazuki Kawano-Furukawa^1,2, and Takatsugu Masuda³

¹RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
²Department of Physics, Advanced Sciences, G.S.H.S. Ochanomizu University, Tokyo 112-8610, Japan
³Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, Tokai, Ibaraki 319-1106, Japan
⁴Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
⁵SNS Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6475, USA

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Vol. 101, Iss. 21 — 1 June 2020

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Figure 1
(a) Schematic structure formed by Co ions in ${YBaCo}_{4} O_{7}$ . (b) $J_{1}$ is the exchange interaction between the Co moments in the kagome lattice. (c) $J_{2}$ is the exchange interaction connecting kagome and triangular lattices. (d) Temperature dependence of the magnetization with $H = 1 T$ . Closed and opened circles show the magnetization on a $δ = 0.15$ sample with $H // a b$ plane and $H // c$ axis, respectively. Closed and opened squares show the magnetization on a $N_{2}$ -annealed sample with $H // a b$ plane and $H // c$ axis, respectively.
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Figure 2
Elastic neutron scattering intensities measured in a CNCS spectrometer. (a) Contour plot of the elastic neutron intensity in the ( $H K$ 0) plane at $T = 10 K$ . (b) Elastic neutron intensities at ( $1.5 - K^{'}, 2 K^{'}, 0$ ) for three $T$ values.
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Figure 3
Neutron scattering intensities measured in a CNCS spectrometer with $E_{i} = 15.1 meV$ . (a)–(c) Contour plots of the inelastic neutron intensities sliced at the energies (a) 4 meV, (b) 7 meV, and (c) 11 meV in the ( $H K$ 0) plane. (d) Contour plots of the inelastic neutron intensities along the ( $H$ ,0,0) at 10 K. (e) and (f) Contour plots of the inelastic neutron intensities sliced at the energies 4 meV in the ( $H K$ 0) plane at (e) 110 K and (f) 300 K. (g) and (h) Contour plots of the inelastic neutron intensities along the ( $H$ ,0,0) at (g) 110 K and (h) 300 K.
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Figure 4
Neutron scattering intensities measured in HRC spectrometer with $E_{i} = 103.4 meV$ at 10 K. (a) and (b) Contour maps of the inelastic-neutron spectra measured at (a) ( $H$ ,0,0) and (b) ( $- 1.5, 0, L$ ).
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Figure 5
(a) and (b) Contour plots of the inelastic neutron intensities sliced at $ℏ ω = 20 meV$ in (a) ( $H K$ 0) and (b) ( $H$ 0 $L$ ) planes. Strong intensities surrounded by dotted lines correspond to the additional background with $| Q | = 4.8 Å^{- 1}$ . (c) $Q$ dependence of the powder-averaged intensity at $ℏ ω = 20 meV$ . The dashed line shows the background intensity estimated in $55 < ℏ ω < 65 meV$ . The solid curve shows the additional background intensity determined by the fitting of the Lorentzian function in the high $Q$ region. The closed circles show the data used in the Lorentzian fitting.
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Figure 6
(a), (c), and (e) Contour plots of $\int ω S_{F}$ in (a) ( $H K$ 0), (c) ( $H$ 0 $L$ ), and (e) ( $H H L$ ) planes. (b), (d), and (f) Upper half of contour plots are the calculated $Q$ dependences of the contrast ratio with first-moment-sum rule in (b) ( $H K$ 0), (d) ( $H$ 0 $L$ ), and (f) ( $H H L$ ) planes. The lower half of the contour plots are the calculated $Q$ dependences of the contrast ratio including the additional back ground intensity. White dashed lines indicate the rough region observed in the experiment.
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Physical Review B

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Magnetic correlations in ${YBaCo}_{4} O_{7}$ on kagome and triangular lattices

Minoru Soda, Shinichi Itoh, Tetsuya Yokoo, Georg Ehlers, Hazuki Kawano-Furukawa, and Takatsugu Masuda

Phys. Rev. B 101, 214444 – Published 29 June 2020

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Physical Review B

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Magnetic correlations in YBaCo4O7 on kagome and triangular lattices

Minoru Soda, Shinichi Itoh, Tetsuya Yokoo, Georg Ehlers, Hazuki Kawano-Furukawa, and Takatsugu Masuda

Phys. Rev. B 101, 214444 – Published 29 June 2020

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Magnetic correlations in ${YBaCo}_{4} O_{7}$ on kagome and triangular lattices