Ⅰ. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 51 (2018)

Eﬀect of Fe substitution on Cu-spin dynamics in the electron-dopedcuprates Eu2−x Cex CuO4+α−δ
Risdiana,∗1 M. Manawan,∗1 Fitrilawati,∗1 L. Safriani,∗1 T. Saragi,∗1 and I. Watanabe∗2
The eﬀect of impurities on the Cu-spin dynamics inhigh-Tc cuprates has attracted great research interestin relation to the mechanism of high-Tc superconductivity. In the hole-doped cuprates of La2−x Srx Cu1−y Zny O4(LSCZO),1,2) the non-magnetic imputity Zn tends toslow down the Cu-spin ﬂuctuations in the whole superconducting regime. In the electron-doped cupratesof the Pr1−x LaCex Cu1−y Zny O4 ,3) on the other hand,
the time spectra are independent of the Zn concentration, which is probably due to the strong effect of the Pr3+ moment. For Ni substitution effects, in La2−x Srx Cu1−y Niy O4 , a hole-trapping effect together with the stripe-pinning eﬀect of Ni wasclearly observed.4) As an electron doped system, weprepared samples without the Pr3+ moment, namely
Eu1.85 Ce0.15 Cu1−y Niy O4+α−δ (ECCNO),5) in order toclarify the eﬀects of Ni on the Cu-spin dynamics. As
shown in Fig. 1, the development of the Cu-spin correlation is induced at low temperatures through Ni substitution. Importantly, in the µSR time spectra of ECCNO,
the trace of the development of the Cu-spin correlation
was observed at low temperatures for the Ni-substituted
samples. However, no clear evidence of the Ni substitution eﬀect on the Cu-spin dynamics has been obtainedyet.
The eﬀect of Fe substitution on Cu-spin dynamics
has attracted much attention owing to the signiﬁcanteﬀect of its large magnetic moment on the superconductivity. In hole-doped systems, it has been found thatthe magnetic transition temperature and magnetic correlation are enhanced through 1% Fe substitution in awide range of hole concentrations at which superconductivity appears in Fe-free La2−x Srx CuO4 .6) On theother hand, the eﬀects of magnetic impurities on theCu-spin dynamics in electron-doped systems have notyet been reported, which prevents us from drawing aclear conclusion on the relation between the dynamical stripe correlations and superconductivity in electrondoped cuprates. Therefore, partial substitution by Fein electron-doped cuprates is a potential method of using an impurity to study the Cu-spin dynamics in theelectron-doped system.
Figure 2 shows the µSR time spectra of
Eu1.85+y Ce0.15−y Cu1−y Fey O4+α−δ (ECCFO) with y =0.005, 0.01, 0.02, and 0.03 at various temperatures. For
all samples, the spectra show an exponential-type depolarization behavior at temperatures below ∼50 K.
Gaussian-type depolarization behavior was only observed at temperatures above ∼200 K, which is higher
than the corresponding temperature of the ECCNO∗1∗2

Department of Physics, Padjadjdaran University, Indonesia
RIKEN Nishina Center- 23 -Fig. 1. µSR spectra of Eu1.85 Ce0.15 Cu1−y Niy O4+α−δ with y= 0, 0.01, 0.02, and 0.05 at various temperatures.5)

Fig. 2. µSR spectra of Eu1.85+y Ce0.15−y Cu1−y Fey O4+α−δ
with y = 0.005, 0.01, 0.02, and 0.03 at various temperatures.

sample at y = 0.02. These results also indicate the traceof development of the Cu-spin correlation. The coherent
precession of muon spins are observed below 50 K, suggesting the existence of a static magnetic ground state.
The trace of stabilization of the Cu-spin ﬂuctuations
by Fe substitution indicates a possibility that the stripe
model can globally explain high-Tc superconductivity asin the case of hole-doped systems.
References
1) T. Adachi et al., Phys. Rev. B 69, 184507 (2004).
2) Risdiana et al., Phys. Rev. B 77, 054516 (2008).
3) Risdiana et al., Phys. Rev. B 82, 014506 (2010).
4) Y. Tanabe et al., Phys. Rev. B 83, 144521 (2011).
5) Risdiana et al., Adv. Mat. Res. 896, 354 (2014).
6) K. M. Suzuki et al., Phys. Rev. B 86, 014522 (2012).