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
課題番号 Project No.

2012A0067

提出日 Date of Report
Jan. 13, 2013
装置責任者 Name of responsible person

実験課題名 Title of experiment

Yasuhiro Miyake

Muon spin researches of valence-trapping and detrapping in mixed-

装置名 Name of Instrument/（BL No.）valence trinuclear carboxylate iron complexes

D1

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Yoichi Sakai

Oct. 24-26, 2012

所属 Affiliation:

Daido 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.
Name:
Mixed-valence trinuclear iron pentafluorobenzoate complex with dichloromethane as crystalline solvent
Chemical form:
Fe3O(C6F5COO)6(C5H5N)3·CH2Cl2(“Fe3”

is “Fe3+Fe3+Fe2+” or “Fe2.7+3”.)

Physical state:
Polycrystalline 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.

The sample Fe3O(C6F5COO)6(C5H5N)3·CH2Cl2 in the present
experiment was prepared by us as a novel compound.
The molecular structure of mixed-valence trinuclear metal carboxylate
complex, M3O(R-COO)6L3 is shown in Figure 1, where L is a ligand suchas pyridine.

The three largest circles are Fe3+ (gray-colored) or Fe2+(white) ions.

Small gray- and black-circles represent C and O atoms,respectively.

R is a pentafluoro-phenyl group, -C6F5.

lines represent the coordination bonds.

The dottedFigure 1

It is shown from our recent

Mössbauer study of this mixed-valence complex that the iron-valence fluctuating rate should be faster than theMössbauer time scale of 140 ns, leading to an average valence of Fe2.7+ at room temperature .[1]Our present experiment was carried out at the MUSE D1 area of MLF/J-parc in order to probe
the valence-fluctuation of tri-iron in the complex using positive muon spin research (μSR)
methods.
12. 実験方法及び結果（つづき） Experimental method and results (continued)
Relaxation of positive muon spin polarization was measured for Fe3O(C6F5COO)6(C5H5N)3·CH2Cl2
over the temperature range of 11 k to 300 K, under a zero magnetic field (ZF) and longitudinalmagnetic fields (LF).

In Figures 2 and 3 are shown the muon spin relaxation curves, the upper(Fig.2) of which are for those at 300 K under LFsof 100, 10 G, and a ZF. The lower (Fig.3) is for
those under a ZF over a wide temperature range

Fig.2

from 11 K to 300 K.
In Figure 2, the following findings were shown;1) Under a ZF at 300 K, spin polarization,
proportional to “Asymmetry” of the ordinate,
was observed to relax (decrease) swiftly.
2) Under a LF of 10 G, about two thirds of muonsrecovered the spin-polarization, which might
be due to decoupling-effect between muon
spins and static nuclear magnetic moments
Fig.3

with a random direction.
3) One third of muon-spins relaxed under LF 10
G was partially (or incompletely) decoupledunder LF 100 G, tentatively being ascribableto the muon component depolarized throughthe magnetic interaction with the fluctuating
electronic

spinoftheFe3O(C6F5COO)6-(C5H5N)3· CH2Cl2 under a ZF orLF 10 G.

The correlation time of muon spin decoupledunder LF 100 G should be estimated 120 ns,Figures 2 and 3 :Time-spectra of positive muon

the Mössbauer excited nuclear level in 57Fe,

spin relaxation ofFe3O(C6F5COO)6(C5H5N)3 ·i.e., the time constant of the electronic-CH2Cl2.

fluctuation of the mixed-valence.

LFs of 100 G, 10 G, and a ZF.

approximately close to the lifetime (140 ns) ofIt might be concluded in the present work
thatwehaveobserved

theelectronic(upper=Fig.2) at 300 K, under(lower=Fig.3) under a ZF, over a temperture
range from 11 K to 300 K .

fluctuation, resulting in the valence detrappingin the mixed-valence complex, by μSR for thefirst time, although further experiments and discussions should be needed.
of the results shown in Figure 3 is under consideration now.
[1].

Y. Sakai

et al.

Hyperfine Interactions, 205, 1-5 (2012)

2The implication