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
2011.07.04
装置責任者 Name of responsible person

課題番号 Project No. 2010B0021

Masahide Harada
実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

High Magnetic Field Neutron Diffractions in Frustrated

BL10Multi-ferroics

実施日 Date of Experiment

実験責任者名 Name of principal investigator2010.02.18-2010.02.19

Hiroyuki Nojiri

2011.03.07-2011.03.11

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.
MnWO4 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.

This proposal is the continuation of the 2010A. In the latter, we have measured the high magnetic
field phase of the multi-ferroic compound BiFeO3 and found that the high field phase isincommensurate. We have also made a short experiment on the multi-ferroic compound MnWO4 up
to 30 T. The data accumulation was poor for the weak intensity of 100 kW. In 2010B, we aimed atcontinuing the experiment on MnWO4.
MnWO4 shows the memory effect in high magnetic field. It consists of zig-zag chains runningalong the c-axis. For the strong spin frustration, three different magnetic phases;AF1(uudd), AF2(non- collinear, incommensurate cycloidal), AF3(incommensurate sinusoidal) appear at zero field.
There are at least three unknown phases in high magnetic fields; HF, IV and V. When a magnetic
field is applied along the easy-axis, a distinct memory effect is found. Namely, the polarization
between the AF2 and IV are always opposite irrespective of the initial polarization. Moreover, thememory is kept while the system is passing through the HF phase, where no polarization exists. The
key experiment to understand the mechanism of the multi-ferroic behavior and the distinct memory
effect in MnWO4 is the determination of magnetic structures in the high magnetic field phases HF,IV and V.
12. 実験方法及び結果（つづき） Experimental method and results (continued)

In the experiment in 2010A and also in a complementary one at SNS-ORNL up to 30 T, we havedetermined that the phase IV is incommensurate and that the HF phase has also small splitting inmagnetic peak. In 2010B, we have first confirmed the pervious result up to 30 T. As shown in Fig. 1,a peak is observed at 4.6 msec by accumulation of data a few hours. This is the commensurate peak.
The sample mounting, test experiment and low field(up to 30 T) were done without trouble before thebreak on 11, March morning.
On March 11, there is a short break of neutron beam delivery during the daytime and then we wereready for the 40 T experiment by 13:00 P.M. When we are filling the He for the restart of the neutron
beam in the evening, the earthquake came and we had to evacuate from the site. So, we could not takethe data at 40 T and we will continue the experiment in 2011A after the finishing of the recovery ofMLF-J-PARC.

Fig. 1 Test data at 30 T.

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