Ⅲ-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 48 (2015)µSR study of the magnetism and superconductivity
in the multi-layered Bi-2223 high-Tc superconductor
T. Adachi,∗1,∗2 M. A. Baqiya,∗3 K. M. Suzuki,∗1,∗4 K. Tsutsumi,∗4 M. Fujita,∗1,∗4 S. Adachi,∗5 T. Watanabe,∗5I. Watanabe,∗1 and Y. Koike∗1,∗3∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
Department of Engineering and Applied Sciences, Sophia
University
Department of Applied Physics, Tohoku University
Institute for Materials Research, Tohoku University
Graduate School of Science and Technology, Hirosaki University

is observed at 0.3 K, indicating the development of theCu-spin correlation. The λ at 0.3 K is more signiﬁcantthan that observed in the underdoped crystals at 0.3
K. Moreover, the temperature dependence of λ exhibits
local maxima at 40 K and 1 K probably corresponding
to the development of the Cu-spin correlation in IPand OP’s, respectively. The temperatures are higher
than those observed in the underdoped crystals, respectively. These results suggest that the Cu-spin correlation is more developed in the HUD crystals than in
the underdoped crystals, although no muon-spin precession due to the formation of a magnetic order isobserved even at 0.3 K. Accordingly, the p value of IP
in the HUD Bi-2223 cuprate may reside in the vicinityof the boundary between the AF and superconducting(SC) phases in the phase diagram.
In summary, we have found two distinct developments of the Cu-spin correlations probably originatingfrom IP and OP’s in the HUD Bi-2223 crystals. Thep value of IP probably resides in the vicinity of theboundary between the AF and SC phases in the phase
diagram, suggesting that the Bi-2223 crystals with Tc
lower than ∼ 40 K exhibit an AF ground state.

Raw Asymmetry (%)

In the research of high-Tc cuprate superconductors,
the relationship between the magnetism and superconductivity has been a central issue. Nuclear-magneticresonance (NMR) experiments in the so-called multilayered Hg-based cuprate Hg-1245 with 5 CuO2 planesin the unit cell have revealed that the hole concentration per Cu, p, in the CuO2 plane is larger in the outerplanes (OP’s) than in the inner planes (IP’s) due to thediﬀerence in the coordination number of Cu between
OP’s and IP’s.1) Moreover, it has been suggested thatboth antiferromagnetic (AF) order and superconductivity coexist homogeneously in a CuO2 plane with asmall p value. In the optimally doped Hg-1245 cuprate,
it has been reported from zero-ﬁeld (ZF) µSR measurements that a muon-spin precession is observed at low
temperatures, suggesting the coexistence of AF orderand superconductivity.2)
Fujii et al.
have succeeded in growing sizable single-crystals of a tri-layered Bi-based cuprate
Bi2 Sr2 Ca2 Cu3 O10+δ (Bi-2223) with Tc = 110 K.3) Recently, we have performed ZF-µSR measurements ofthe underdoped Bi-2223 single-crystals with Tc = 87
K, obtained through the reduction annealing. It has
been found that the depolarization rate of muon spins,
λ, increases with decreasing temperature and exhibits
a local maximum at 10 K, followed by an increase below 5 K. This suggests the existence of two distinct
Cu-spin correlations in a crystal probably originatingfrom IP and OP’s. However, the development of theCu-spin correlation is weak even at 0.3 K, preventing
us from investigating the detailed magnetic state inBi-2223 cuprates. Based on the results, we have performed µSR measurements of Bi-2223 in the heavily
underdoped (HUD) regime with Tc = 40 − 60 K, obtained through the further reduction-annealing. TheZF and longitudinal-ﬁeld µSR measurements were carried out using a ﬂy-past HELIOX cryostat at temperatures down to 0.3 K at RIKEN-RAL.
Figure 1 shows ZF spectra of the HUD Bi-2223. At250 K, the spectrum shows a slow depolarization ofmuon spins, indicating that Cu spins ﬂuctuate fast beyond the µSR frequency range. With decreasing temperature, it is found that the depolarization becomes
fast gradually and an exponential-like depolarization

20Bi2Sr2Ca Cu O10+δδ15Heavily underdoped(Tc = 40 - 60 K)
Zero field2310
T = 250 K
40 K
2K
20 K
1K
5 K 0.3 K

50246810

12Time (µµsec)
Fig. 1. Zero-field µSR time spectra of the heavily underdoped Bi2 Sr2 Ca2 Cu3 O10+δ single crystals with Tc =40 − 60 K.

References
1) H. Mukuda et al.: J. Phys. Soc. Jpn. 77, 124706(2008).
2) K. Tokiwa et al.: Physica C 460-462, 892 (2007).
3) T. Fujii et al.: J. Cryst. Growth 223, 175 (2001).

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