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。 ）提出日 Date of Report

MLF Experimental Report
課題番号 Project No.

装置責任者 Name of responsible person

2014A0198

Yasuhiro Miyake

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）SR study of the possible ferromagnetic state in the heavily

D1

overdoped Bi-2201 high-Tc superconductor

実施日 Date of Experiment

実験責任者名 Name of principal investigator

2015. 11. 19 – 22

Tadashi Adachi
所属 Affiliation
Department of Engineering and Applied Sciences, Faculty ofScience and Technology, Sophia 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.

Bi-based high-Tc superconducting cuprates
Bi1.71Pb0.32Sr1.97CuO6+
Single crystals

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.

Zero-field and longitudinal-field SR measurements have been performed using the dilution refrigerator attemperatures between 72 mK and 2 K and in magnetic fields up to 200 G for non-superconducting heavily
overdoped Bi1.71Pb0.32Sr1.97CuO6+ (Bi-2201) single crystal.

Measurements have been performed in thedouble-pulsed mode.
On the first and second days, the dilution refrigerator was in trouble and the temperature did not reach below
2 K.

On the third trial, the temperature reached at 72 mK.

The reason of the trouble is probably tiny leak of

the vacuum around the window of the dilution refrigerator where muons come into.
one day for the measurements.

1Therefore, we had only2. 実験方法及び結果（つづき） Experimental method and results (continued)
From the zero-field SR measurements, it has been found that the spectra are Gaussian-like more or less for
all temperatures.

At the lowest temperature of 72 mK, it has been found that the spectrum tends to deviateslightly from the Gaussian-like behavior at 2 K, suggesting that the spin correlation is slightly developed at 72mK.
We have analyzed the spectra using the function: A(t) = A0 exp[-t] GZ(,t) + ABG, where  is thedepolarization rate of muon spins and GZ(,t) is the static Kubo-Toyabe function.
time-independent background term.

The ABG is theAs shown in the figure, it has been found that  increases with decreasing

temperature below ~ 0.7 K, suggesting the development of the spin correlation.
Combined with the electrical-resistivity and magnetization results [1], the present SR results suggest thatthe ferromagnetic correlation is developed at low temperatures in the non-superconducting heavily overdoped
Bi-2201.

Therefore, the ferromagnetic fluctuation might be related to the disappearance of thesuperconductivity in the heavily overdoped high-Tc cuprates.
[1] K. Kurashima, T. Adachi, K. M. Suzuki, Y. Fukunaga, T. Kawamata, T. Noji and Y. Koike, J. Phys.: Conf.
Series 568, 022003 (2014).

Bi1.71Pb0.32Sr1.97CuO6+

 (10-2 sec-1)

5

Non-superconducting
heavily overdoped

4

32A(t) = A e-λt Gz(Δ,t)
100.5

1.0

1.5

2.0T (K)
Figure: Temperature dependence of the depolarization rate of muon spins, , in non-superconducting
heavily overdoped Bi1.71Pb0.32Sr1.97CuO6+ single crystal.

2