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 Report2017.4.13

課題番号 Project No.

装置責任者 Name of responsible person

2016B0052

Shinichi Itoh

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Investigation of excitations in Nd-based metallic materials

BL12 (HRC)

exhibiting heavy-fermion natures

実施日 Date of Experiment

実験責任者名 Name of principal investigator2017.2.9 – 2.13

Kazuaki Iwasa

2017.2.21 - 2.26

所属 Affiliation
Frontier Research Center for Applied Atomic Sciences & Instituteof Quantum Beam Science, Ibaraki 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.
NdFe4P12 single crystal
NdRu4P12 powder
NdO0.5F0.5BiS2 powder

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.

Filled-skutterudite compounds, NdFe4P12 (L. Keller et al., J. Alloys and Comp. 323–324, 516 (2001)) andNdRu4P12 (H. Sugawara and C. Sekine, private communication, S. Masaki et al., PRB 78, 094414 (2008)), exhibit
ferromagnetic ordering at 1.9 and 1.6 K, respectively. The electrical-resistivity data of NdFe4P12 show anincrement with decreasing temperature below approximately 20 K (H. Sato et al., PRB 62, 15125 (2000)). Thisbehavior is considered to be caused by the Kondo effect because the observed phenomenon is reproduced bya function of temperature, –logT. A less significant anomaly in the resistivity was found for NdRu4P12 (T.
Utsumi et al., Muroran Inst. Tech. Journal 49, 93 (1999) (in Japanese)). We are also interested in
NdO0.5F0.5BiS2, which is a family of the layered BiS2-based superconductors. The specific heat divided bytemperature (C/T) reaches a high value of 7.5 J/(K2 mol) at 0.3 K, and the magnetic susceptibility saturates in
the low-temperature region (T. D. Matsuda, Y. Mizuguchi, Y. Aoki, private communication). In order toinvestigate electronic hybridization between rare-earth 4f electrons and conduction electrons in thesecompounds, we performed inelastic neutron scattering (INS) experiments at low-temperature region.
12. 実験方法及び結果（つづき） Experimental method and results (continued)
Figure 1 shows an intensity contour map in the Q-E space of NdFe4P12 at 5 K, which is obtained bysubtracting the empty-sample-cell data from the sample measurement data. The incident neutron energy was
82 meV. A strong peak is located at 28 meV in the80

lower Q region below 3 Å-1, This excitation is flat withrespect to Q, and the intensity decreases with2017.2.9 HRC (BL12) @ MLF
NdFe4P12 – Empty cell
4 K GM cryo
Ei = 81.92 meV(400 Hz, 3570 µsec)
3K60

increasing temperature. Thus this excitation seems

0.00080.000640

crystalline-electric-field (CEF) levels. In addition,
gradual change of scattering intensities in the same

E (meV)

to be caused by magnetic scattering between
200.0004

00.0002

Q-region with decreasing the energy can be seen.
-20

These results may indicate that the broadening ofthemagneticexcitations

inNdFe4P12,

asa0.0000-40

consequence of hybridization effect between the Nd

04f electrons and conduction electrons in the2468-1Q (Å )heavy-fermion (HF) state. On the other hand, weFig. 1 Intensity contour map in the Q-E space ofobserved stronger intensities in the Q region above 3NdFe4P12 at 5 K.

Å-1, which might be due to phonon contribution.

Figure 2 shows an intensity contour map in the Q-E space of NdO0.5F0.5BiS2 at 3 K. The incident energy was51 meV. We observed Q-independent excitation peaks at 8.5 and 13 meV, the intensity of which decrease withincreasing temperature. We also observed scattering intensities located at 23 meV, which are two-peakstructure with respect to energy. The temperaturedependence of this signal is not distinct between 3

2017.2.9 HRC (BL12) @ MLF
NdO0.5F0.5BiS2 powder, 4 K GM cryo
Ei = 50.98 meV(400 Hz, 2020 µsec)
Background subtracted
3K40

and 100 K, but the Q-flat intensity is consistent with0.0015

the CEF excitation. These excitations can bedoublets expected from the local symmetry of the Ndions in NdO0.5F0.5BiS2. It is undertaken to identify the200.0010

00.0005-200.0000

E (meV)

explained by transitions between the five CEF

level scheme. In addition, spectral widths of these
excitations are close to the instrumental resolution.
This fact suggests that the 4f electrons are well
localized to the Nd ion, in contrast to broad

0123

456-1

excitation peaks due to electronic hybridization often

Q (Å )

seen in conventional HF materials. It is attractive toFig. 2 Intensity contour map in the Q-E space ofinvestigate how the large value of C/T appears.

NdO0.5F0.5BiS2 at 3 K.

2