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.

装置責任者 Name of responsible person

2017A0010

Shinichi Itoh

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Determination of dispersion relation of magnetic excitations in theHRC (BL12)

antiferromagnetic alternating spin-3/2 chain compound NdCrTiO5

実施日 Date of Experiment

実験責任者名 Name of principal investigator

May 25 to 27, 2017

Masashi Hase所属 Affiliation
National Institute for Materials Science
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.
NdCrTiO5 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.
3+

It is expected that Cr

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

spins form an antiferromagnetic (AF) alternating spin-3/2 chain in NdCrTiO5. Theground state (GS) of the chain is a spin-singlet state. A spin gap exists between the GS and first excited tripletstates. Both Cr and Nd moments, however, are ordered simultaneously at the transition temperature TN = 21 K.
In previous HRC experiments (Project No.:2012B0009), we observed a large spin gap (20 meV) in theisostructural compound NdCrGeO5. The transition temperature is low (TN = 2.5 K). It is not confirmed whether
Cr moments are ordered or not. We infer that a probably small spin gap leads to the high TN in NdCrTiO5 Inorder to investigate magnetic excitations in NdCrTiO5, we performed inelastic neutron scattering (INS)experiments on NdCrTiO5 powder using the HRC spectrometer.
Figure 1(a) shows an INS intensity map in the Q- plane at 3.5 K. The energy of incident neutrons (Ei) is 51.2
meV. We can see strong excitations around  = 6.9 meV and Q = 1.2 Å-1. The Q value is consistent with that ofthe zone center of the Cr spin-3/2 chain. As inferred, the spin gap of NdCrTiO5 is small. Excitations around Q =1.2 Å-1 exist up to 20 meV. We will determine the dispersion relation of the magnetic excitations along the spin
chain using the conversion method developed by Tomiyasu et al. Excitations around 20 meV and 28 meV remain
up to high Q. Probably, these are crystal-field excitations of Nd. Similar excitations were observed in NdCrGeO5.

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2. 実験方法及び結果（つづき） Experimental method and results (continued)
Figure 1(b) shows an INS intensity map at 3.5 K obtained using neutrons of Ei = 11.5 meV. Excitations exist
around 3.4 and 5.5 meV. These excitations were observed in the data obtained using neutrons of Ei = 8.2 meV.
Therefore, these are excitations of NdCrTiO5. The excitations around 3.4, 5.5, and 6.9 meV shows a similar Q
dependence. Probably, the excitations around 3.4 and 5.5 meV originate from Cr spins. We will consider theorigin of these excitations. Excitations around 2 meV remain up to high Q. Probably, these are also crystal-field
excitations of Nd.
We also performed INS experiments at 10.4, 15.4, 21.0, 26.0, and 200 K. Figures. 1(c) and (d) show an INS
intensity map at 15.4 K obtained using neutrons of Ei = 11.5 and 51.2 meV, respectively. As the temperature israised, the excitations between 6 and 20 meV seem to be shifted to lower energies. Similar temperaturedependence was observed in compounds having a spin gap and AF order. Examples are the spin 1/2 tetramer
compound Cu2CdB2O6 and the spin 3/2 dimer compound CrVMoO7. We will consider the origin of thetemperature dependence.

Fig 1INS intensity maps of NdCrTiO5 powder. The vertical and horizontal axes show the transfer

energy and scattering vector magnitude, respectively.

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