実験報告書様式（一般利用課題・成果公開利用）

MLF Experimental Report

提出日 Date of Report

課題番号 Project No.

装置責任者 Name of responsible person

2017A0143

Takashi Kamiyama

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Detailed structure analysis on perfect kagome compound

SuperHRPD (BL08)

Li2Cr3SbO8

実施日 Date of Experiment

実験責任者名 Name of principal investigator

2017/4/14 – 2017/4/18

Kazuki Iida所属 Affiliation
CROSS
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
Polycrystalline Li2Cr3SbO8.

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

Macroscopic ground-state degeneracy in highly frustrated magnets can lead to unconventional magnetic
behaviors such as the classical/quantum spin liquid. Recently, we succeeded in making a new kagome compound
Li2Cr3SbO8, and Li2Cr3SbO8 undergoes so-called √3 × √3 long-range magnetic order below TN = 4.5 K. We
already performed neutron diffraction measurements, but the resolution was not sufficient to determine thedetailed “crystal” structure. Since the detailed crystal structure is important to discuss the properties of frustratedsystems, investigation on the detailed crystal structure of Li2Cr3SbO8 using SuperHRPD is purpose of thisexperiment.
We prepared 2.2 g high-quality polycrystalline Li2Cr3SbO8 sample for the neutron diffraction measurements.
The sample was put into the vanadium can, which was attached to the bottom loading cryostat. The measurements
were performed at T = 4.7, 7, 10, 20, 60, 100, 150, 200, and 300 K. We mainly used the data obtained by thebackscattering (BS) bank. Data was analyzed by the ZRietveld software.
Figure 1 shows the neutron diffraction result from the BS bank at 4.7 K together with the Rietveld refinement
results. The refined crystal parameters are summarized at Table I, and the obtained crystal structure is described in1

2. 実験方法及び結果（つづき） Experimental method and results (continued)
Fig. 2. The results show that the kagome lattice in Li2Cr3SbO8 is not a perfect kagome but slightly distorted. The
difference between the two different nearest neighbor distances is about 5.02%. Interestingly, the crystal structure
is a so-called breathing kagome, where the small and large triangles align alternatively. Furthermore, theweathervane mode which is the most interesting features of √3 × √3 kagome structures still exists in the breathing
kagome structure realized in Li2Cr3SbO8. Therefore, although the kagome lattice in Li2Cr3SbO8 is slightly
distorted, Li2Cr3SbO8 still has the most important feature originating from the geometrical frustration.
Finally, we appreciate the local contacts at SuperHRPD for their kindness support.

Figure 1. The neutron powder diffraction pattern at 4.7 K in Li2Cr3SbO8 obtained from the BS bank at
SuperHRPD together with the Rietveld refinement results using ZRietveld. Figure 2. Obtained crystal structure ofLi2Cr3SbO8. Only the Cr site is shown.
xyz

Biso (Å2)

AtomOccupancyCr1

0.17095(7)0.82905(7)0.2478(7)0.377539

Li110.33333

0.66667

0.93649(3)0.734892

Li21000.52546(3)0.963648

O1

1000.34047(10)0.397386

O2

10.33333

0.66667

0.13955(9)0.498587

O3

1

0.48167(4)0.51833(4)0.37779(6)0.450468

O4

1

0.16604(10)0.83396(10)0.62995(7)0.436658

Sb

10.33333

0.66667

0.5228(10)0.326869

Table I. The refined crystal structure parameters at 4.7 K in Li2Cr3SbO8. We assumed the P63mc space group. The
refined crystal parameters are a = b = 5.83269(1) Å and c = 9.504188(3) Å.

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