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
2014/7/16

課題番号 Project No.

装置責任者 Name of responsible person

2014A0186

Shuki Torii

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Magnetic structure of ferrimagnetic spinel compound CoV2O4

BL08

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Hiroki Ishibashi

2014/5/16 21:00 – 2014/5/20 21:00

所属 Affiliation
Osaka Prefecture 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.
cobalt vanadate (CoV2O4) 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.

Spinel vanadium oxide CoV2O4 shows ferrimagnetic transition at TC = 145 K and another transition is observed
at T1 = 60 K, however, the origin of the transition at T1 as well as the magnetic structure of CoV2O4 is stillunclear.
Neutron powder diffraction experiments were performed using a time-of-flight (TOF) diffractometer at
BL08 beamline. The temperature dependence of the powder patterns of CoV2O4 was measured in thetemperature range of 10 – 300 K using a closed-cycle refrigerator. We measured the diffraction patterns withlong scan time (10 h) at 160 K, 70 K and 10 K (set temperature) corresponding to the paramagnetic and two
ferrimagnetic phases, respectively, to refine the magnetic structure and those with short scan (2 h) toinvestigate the temperature dependences of lattice constant and intensities of the magnetic reflections.
Figure 1 shows a part of the powder diffraction patterns at 12, 81 and 171 K (sample temperature) obtainedby the back scattering bank. All peaks can be indexed with the space group Fd-3m, and neither forbidden
reflection nor superlattice one was detected in the diffraction pattern. This result indicates that the clear
structural phase transition does not occur in CoV2O4 unlike the similar compound such as MnV2O4.
1

2. 実験方法及び結果（つづき） Experimental method and results (continued)
Figure 2 shows the temperature dependence of the lattice constant estimated by the peak positions of theBragg reflections. An anomalous behavior is clearly observed at around T1, which may correspond to the phasetransition at T1.
On the other hand, intensities of some peaks such as 220 and 311 reflections change with decreasing
temperature as shown in Fig. 1. Figure 3 shows the temperature dependences of the intensities of 220 and 311
reflections. Abrupt increases in the intensities are observed at the ferrimagnetic transition temperature TC =145 K, caused by the magnetic ordering. However, it is unclear whether there is an anomaly at T1. We
constructed the magnetic structure model of the ferrimagnetic phases based on the space group Fd-3m withthe propagation vector k = (0, 0, 0) in order to refine them by the Rietveld method. The simplest model is thecollinear configuration one, i.e., the magnetic moment of Co2+ is antiparallel to that of V3+. We carried out theRietveld analysis by assuming the collinear model using the FullProf program. Figure 4 shows the result of theRietveld fitting of the data at 81 K, and the fitting is almost good. The refined magnitudes of the magnetic
moments of Co2+ and V3+ are 2.60(2) and 0.45(3) B, respectively, which indicates that V3+ has much smaller
magnetic moment than that expected from the spin moment (2 B). The analysis based on of the non-collinear

141500142000TOF (s)

220
311

171 K
81 K
12 K

80000

100000120000TC

8.408

Lattice constant a (Å)

400

141000

T1

171 K
81 K
12 K

220

331

440511, 333
422

Intensity (arb. units)

222

model is now in progress.

8.406
8.404
8.402
8.40140000

TOF (s)100
Temperature (K)200Fig. 2. Temperature dependence ofFig. 1. Neutron powder diffraction patterns oflattice constant of CoV2O4.

CoV2O4 at 12, 81, and 171 K.
T1

TC

Intensity (arb. units)

220
311

0100
200
Temperature (K)Fig. 3. Temperature dependence of theFig. 4. Observed and calculated diffraction patterns at 81 K

intensities for 220 and 311 Bragg peaks.

from the Rietveld refinement.

intensities.

2