Neutron scattering study on dimerized $4{f}^{1}$ intermetallic compound ${\mathrm{Ce}}_{5}{\mathrm{Si}}_{3}$

Neutron scattering study on dimerized $4 f^{1}$ intermetallic compound ${Ce}_{5} {Si}_{3}$

Daichi Ueta, Yuki Iwata, Riki Kobayashi, Keitaro Kuwahara, Takatsugu Masuda, and Shinichi Itoh

Phys. Rev. B 109, 205127 – Published 9 May 2024

Abstract

${Ce}_{5} {Si}_{3}$ exhibits geometrical frustration in its crystal structure and possesses a Schottky-type anomaly, implying dimer formation based on specific heat measurements. We performed inelastic neutron scattering experiments on polycrystalline samples to observe microscopical evidence of dimer formation. Crystalline electric field excitations were observed at 17, 27, 39, and 63 meV, and magnetic excitation caused by spin-dimer formation with dispersion was observed at approximately 0.6 meV. The magnetic excitation observed at low energies may originate from spin-dimer formation, which exhibits large dispersion that cannot be explained using the conventional Shastry–Sutherland lattice model, implying that the excited-state pseudotriplet may split.

Received 21 July 2023
Revised 2 March 2024
Accepted 22 April 2024

DOI:https://doi.org/10.1103/PhysRevB.109.205127

Physics Subject Headings (PhySH)

Magnetism

Metals

Neutron scattering Time-of-flight neutron spectroscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Daichi Ueta ^1,*, Yuki Iwata², Riki Kobayashi ², Keitaro Kuwahara³, Takatsugu Masuda ^1,4, and Shinichi Itoh ¹

¹Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
²Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara-cho 903-0123, Japan
³Graduate School of Science and Engineering, Ibaraki University, 2-1-1 Mito, Ibaraki 310-8512, Japan
⁴Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan

^*dueta@post.kek.jp

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Vol. 109, Iss. 20 — 15 May 2024

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Figure 1
(a) Crystal structure of ${Ce}_{5} {Si}_{3}$ illustrated using VESTA [23]. Blue and brown balls exhibit the cerium atoms, and silver balls exhibit the silicon atoms. (b) SSL cerium layers at the $a b$ plane. The green broken line connects the nearest-neighbor atoms in the SSL. (c) CEF splitting in ${Ce}^{3 +}$ ions and splitting of the ground-state doublet due to spin-dimer formation at the Ce(2) site.
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Figure 2
Color-coded plots of INS intensities measured on the HRC with $E_{i}$ = 153 meV for (a) ${Ce}_{5} {Si}_{3}$ , (b) ${La}_{5} {Si}_{3}$ , and (c) magnetic scattering of ${Ce}_{5} {Si}_{3}$ at 15.3 K. The insets show the data above 50 meV with the color scale changed to clarify the excitation. (d) A section of magnetic scattering integrated over $| Q |$ from 2.0 to 3.0 $Å^{- 1}$ . The black solid line shows the fitting results, and the dashed lines represent the fitting components of the elastic scattering and CEF excitations, respectively. The vertical bars represent the statistical errors. The CEF level scheme of ${Ce}_{5} {Si}_{3}$ at (e) Ce(1) and (f) Ce(2) sites evaluated based on the analysis of the INS data.
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Figure 3
(a) $| Q |$ dependence of magnetic scatterings observed at around $E$ = 17.1 (red), 26.5 (blue), 38.8 (green), and 62.9 (purple) meV and behavior of magnetic form factor of ${Ce}^{3 +}$ ions. (b) Energy dependence of magnetic scattering intensity of ${Ce}_{5} {Si}_{3}$ at 15.3 K (red circles) and 1.0 K (blue circles). The black solid line and the black broken lines show the fitting results at 15.3 K and 1.0 K, respectively. The CEF parameters and levels obtained from this fitting are listed in Table 1. The vertical bars in (a) and (b) represent the statistical errors.
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Figure 4
(a) Temperature dependence of the reciprocal magnetic susceptibility of ${Ce}_{5} {Si}_{3}$ . The red circles and blue triangles denote the measurement data for $H$ // [110] and [001], respectively, and the black solid lines were calculated using the CEF model. (b) Temperature dependence of the reciprocal magnetic susceptibility of the Ce(1) site (solid lines) and Ce(2) site (broken lines). The red and blue lines show the calculation results of $H$ // [110] and $H$ // [001], respectively.
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Figure 5
Color-coded plots of INS intensity measured on HRC with $E_{i} = 3$ meV for (a) ${Ce}_{5} {Si}_{3}$ and (b) ${La}_{5} {Si}_{3}$ , and (c) magnetic scattering of ${Ce}_{5} {Si}_{3}$ at 0.3 K. (d) Temperature evolution of magnetic excitation at $| Q | = 0.2 Å^{- 1}$ . (e) Energy dependence of magnetic peaks at $| Q |$ . The data were vertically shifted for clarity, and the dashed lines represent the origin of the vertical axis of the corresponding data. The solid lines represent the results of fitting each data with a Gaussian function, and the solid black triangles indicate the respective peak positions. The vertical bars in (d) and (e) represent statistical errors. (f) Temperature dependence of magnetic specific heat divided by temperature (red circles; left axis) and magnetic entropy (green triangles; right axis). The blue broken line and black solid line show the calculation curve when the excited pseudotriplet is assumed to be degenerate and not degenerate, respectively.
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Physical Review B

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Neutron scattering study on dimerized $4 f^{1}$ intermetallic compound ${Ce}_{5} {Si}_{3}$

Daichi Ueta, Yuki Iwata, Riki Kobayashi, Keitaro Kuwahara, Takatsugu Masuda, and Shinichi Itoh

Phys. Rev. B 109, 205127 – Published 9 May 2024

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Physical Review B

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Neutron scattering study on dimerized 4f1 intermetallic compound Ce5Si3

Daichi Ueta, Yuki Iwata, Riki Kobayashi, Keitaro Kuwahara, Takatsugu Masuda, and Shinichi Itoh

Phys. Rev. B 109, 205127 – Published 9 May 2024

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Neutron scattering study on dimerized $4 f^{1}$ intermetallic compound ${Ce}_{5} {Si}_{3}$