実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF	 Experimental Report

提出日 Date of Report

課題番号 Project No. 2014A0298

装置責任者 Name of responsible person

実験課題名 Title of experiment

Takashi Ohara

High Magnetic Field Neutron Diffraction in Shastry-Sutherland

装置名 Name of Instrument/（BL No.）

System - Step 2BL18

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Hiroyuki Nojiri

2014.11.5-11.10

所属 Affiliation
Institute for Materials Research, Tohoku University
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.

SrCu2(BO3)2 single crystal

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.
We have made the second experiment by using a wide-angle solenoid coil generating 40 T and have achieved
several improvements from the 1st experiment of the proposal 2012B0147. The final goal of this experiment is toinvestigate the magnetization plateaus observed in quasi two-dimensional materials. The sample is the Shastry
and Sutherland lattice and the realization is found in SrCu2(BO3)2. The compound has a unique orthogonalarrangement of dimers in two-dimension. For the frustration between the nearest neighbor and the next-nearest
neighbor interactions, the effective repulsive interaction acts among triplets. The hopping of triplets is strongly
suppressed for the orthogonal dimer network. These two special conditions result in the formation of plateau
state.
In the present experiment, we have investigated the 1/8 plateau appearing at around 28.5 T and the state above
1/8 plateau. Combining our new capacitor bank and the wind-angle solenoid, we can access to 40 T. Figure 1
shows the new capacitor bank of 90 kJ storing energy. It can be set in the limited space of BL18. The
temperature was cooled down to 2 K, which is limited by the power of the pump for 4He-depressering. This
point must be improved by using larger pump and/or the 3He system in the next experiment.
Figure 2 shows the TOF spectrum in (h,0,0) zone. The pulsed magnetic field is applied to the index of (7/8 0 0).
We could not found magnetic Bragg peak in this setting. Although a fast adiabatic cooling effect is expected inpulsed magnetic fields, it is unclear at present if the wave vector for 1/8 plateau phase is different or thetemperature was not low enough.

12. 実験方法及び結果（つづき） Experimental method and results (continued)
Figure 3 shows the TOF spectrum at 32. 6 T, which is located between 1/8 and 1/4 magnetization plateaux. We
found no peak in this condition.

Fig. 1 New 90 kJ Capacitor Bank

Fig. 2 TOF Spectrum at 28.4 T

Fig. 3 TOF Spectrum at 32.6 T
To be summarized, in the step II experiment, we could reach the 1/8 plateau and the state between 1/8 and1/4 plateaux. However, no magnetic peak was found in high magnetic fields. At this moment, it is not clear, if
the wave vector is not in the (h 0 0) zone or not. On the other hand, we could take the TOF spectrum in highmagnetic fields including (200) and (400). The estimate of the intensity of magnetic Bragg peaks proposed bydifferent models is in progress for the step III experiment. Since we can access the magnetic field above 30 T
now, we are going to introduce the 3He low temperature device in the next step.

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