日本原子力研究開発機構機関リポジトリ
Japan Atomic Energy Agency Institutional Repository

Title

Revising the 4ƒ symmetry in CeCu 2 Ge 2 ; Soft X-ray absorption andhard X-ray photoemission spectroscopy
Aratani Hidekazu, Nakatani Yasuhiro, Fujiwara Hidenori,
Kawada Moeki, Kanai Yuina, Yamagami Kohei, Fujioka Shuhei,
Hamamoto Satoru, Kuga Kentaro, Kiss Takayuki,

Author(s)Yamasaki Atsushi, Higashiya Atsushi, Kadono Toshiharu,
Imada Shin, Tanaka Arata, Tamasaku Kenji, Yabashi Makina,
Ishikawa Tetsuya, Yasui Akira, Saito Yuji, Narumi Yasuo,
Kindo Koichi, Ebihara Takao, Sekiyama Akira

Citation
Text Version

Physical Review B,98(12),p.121113_1-121113_6
Version of Record

URL

https://jopss.jaea.go.jp/search/servlet/search?5063836

DOI

https://doi.org/10.1103/PhysRevB.98.121113

Right© American Physical Society

Japan Atomic Energy Agency

PHYSICAL REVIEW B 98, 121113(R) (2018)
Rapid Communications

Revising the 4 f symmetry in CeCu2 Ge2 : Soft x-ray absorption
and hard x-ray photoemission spectroscopy
H. Aratani,1,2 Y. Nakatani,1,2 H. Fujiwara,1,2,* M. Kawada,1,2 Y. Kanai,1,2 K. Yamagami,1,2 S. Fujioka,1,2 S. Hamamoto,1,2
K. Kuga,2 T. Kiss,1,2 A. Yamasaki,2,3 A. Higashiya,2,4 T. Kadono,2,5 S. Imada,2,5 A. Tanaka,6 K. Tamasaku,2 M. Yabashi,2T. Ishikawa,2 A. Yasui,7 Y. Saitoh,8 Y. Narumi,9,† K. Kindo,9 T. Ebihara,10 and A. Sekiyama1,2
1Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
2
RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan
3
Faculty of Science and Engineering, Konan University, Kobe 658-8501, Japan
4
Faculty of Science and Engineering, Setsunan University, Neyagawa, Osaka 572-8508, Japan
5
Department of Physical Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan
6
Department of Quantum Matter, ADSM, Hiroshima University, Higashi-hiroshima, Hiroshima 739-8530, Japan
7
Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo 679-5198, Japan
8
Materials Sciences Research Center, Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148, Japan
9
The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan10
Department of Physics, Shizuoka University, Shizuoka 422-8529, Japan(Received 6 February 2018; revised manuscript received 6 September 2018; published 28 September 2018)
We present a detailed study on the 4f ground-state symmetry of the pressure-induced superconductor
spectroscopy. The revised Ce
CeCu2 Ge2 probed by soft x-ray absorption√and hard x-ray photoemission√
4f ground states are determined as |7  = 0.45 |Jz = ± 25  − 0.55 |∓ 23  with -type in-plane rotational
symmetry. This gives an in-plane magnetic moment consistent with the antiferromagnetic moment as reported
in neutron measurements. Since the in-plane symmetry is the same as that for the superconductor CeCu2 Si2 ,we propose that the charge distribution along the c axis plays an essential role in driving the system into asuperconducting phase.
DOI: 10.1103/PhysRevB.98.121113

The discovery of the first heavy fermion superconductor
CeCu2 Si2 has attracted considerable attention to quantum critical phenomena in strongly correlated electron systems [1–4]such as high-Tc superconductivity and topological phases withstrong spin-orbit interactions [5,6]. The superconductivity in
CeCu2 Si2 is suppressed by the isostructural substitution of Ge
for Si [7,8]. The end-member compound tetragonal CeCu2 Ge2shows an antiferromagnetic long-range order below a Néel
temperature (TN ) of ∼4.2 K at ambient pressure [9]. The
Sommerfeld coefficient γ is as high as 100 mJ/(mol K2 ), suggesting that the energy scale of the on-site Kondo fluctuationis the same order of magnitude as that of the Ruderman-KittelKasuya-Yosida (RKKY) interaction [9]. An external pressure
above 7.6 GPa induces superconductivity below 0.6 K due
largely to an increase of the hybridization between the localized 4f and conduction electrons. Moreover, a different typeof superconducting phase emerges at around 12 GPa, wherean abrupt change into the critical 4f valence fluctuation in
the presence of a strong on-site Coulomb repulsion has been
proposed to understand its origin [10–12].
The low-temperature properties of these compounds
are mostly determined by the 4f ground-state*

fujiwara@mp.es.osaka-u.ac.jp
Present address: Center for Advanced High Magnetic Field Science, Graduate School of Science, Osaka University, Toyonaka,
Osaka 560-0043, Japan.
†

2469-9950/2018/98(12)/121113(6)symmetry for Ce3+ ions in the tetragonal crystalline electricfield (CEF). The 4f states with a total angular momentum
J = 5/2 split into three Kramers doublets
equated to√|6  = |Jz = ± 21 , |71  = α |± 25  − 1 − α 2 |∓ 23 , and√|72  = 1 − α 2 |± 25  + α |∓ 23 , where α 2 denotes the
mixing factor reflecting the out-of-plane (parallel to the
crystal c axis) anisotropy in the spatial distribution of the 4f
states. The α 2 value is also connected to the anisotropy inmagnetic moments per Ce ion as shown in Fig. 1 [13,14].
The out-of-plane anisotropy can be determined by linearlypolarized soft x-ray absorption spectroscopy (XAS) [15–17],
and the phase diagram of tetragonal CeIr 1−x Rhx In5 has shown
to be scaled by α 2 [17]. Therefore, it has been recognizedthat proving ground-state symmetry is of great importanceto elucidate the origin of quantum critical phenomena. In
addition, the sign of α gives the in-plane (perpendicular tothe c axis) rotational symmetry labeled as -type (-type)
7 , whose charge distribution has valleys (crests) in the[100] direction as shown in Fig. 1(b). The in-plane symmetry
for both CeCu2 Si2 and CeCu2 Ge2 has been determinedas -type 7 using nonresonant inelastic x-ray scattering(NIXS) [18,19].
However, the CEF ground-state symmetry of CeCu2 Ge2is still puzzling. It has been reported that the 4f symmetry is described as |7  = 0.9 |± 25  ± 0.435 |∓ 32  [20]. The
corresponding α 2 value of 0.81 yields an expected magnetic
moment of ∼1.5μB /Ce along the c axis as obtained from121113-1©2018 American Physical Society

H. ARATANI et al.

PHYSICAL REVIEW B 98, 121113(R) (2018)

(a)

[001]

(b)

c

a
a

FIG. 1. (a) Expectation values of magnetic moments along the3+denoted as Ma and Mc for thea and c axes per√ a Ce ion
52|7  = α |± 2  ± 1 − α |∓ 23  ground states plotted as a functionof α 2 . Dashed lines are guides for the eye for α 2 = 0.45 and 0.81.
(b) Angular distribution of charge density plot of the 7 states withthe possible rotational symmetry of  type (left) and  type (right).
In the HAXPES measurements, the angle between the incoming x
ray (projection from an outgoing photoelectron to the ab plane) andthe [001] direction ([100] direction) is defined as θ (φ).

Fig. 1, which is much larger than a magnetic ordered momentof 1.04μB /Ce below TN observed in neutron measurements[21–23]. It is also in sharp contrast to the Ce moments
pointing in the ab plane [22,23]. Therefore, it is essential
to determine the 4f ground-state symmetry of CeCu2 Ge2 byutilizing advanced spectroscopy.
In this Rapid Communication, we report a revising groundstate symmetry of CeCu2 Ge2 studied by the polarized XAS
and hard x-ray photoemission spectroscopy (HAXPES). The
mixing parameter α 2 , obtained by XAS, successfully explains
the magnetic susceptibility. By analyzing the Ce 3d corelevel HAXPES spectra using the same α 2 value [24–26],
in-plane symmetry of the 4f states is determined as -type
7 , which is consistent with the results obtained from NIXS
measurements [19].
High-quality CeCu2 Ge2 single crystals were grown by
the Cu-Ge flux method [27]. Magnetic susceptibility wasmeasured by means of a superconducting quantum interface
device (SQUID) magnetometer (Quantum Design, MPMS3).
XAS measurements were performed at the twin-helical undulator beamline BL23SU of SPring-8 [28]. The XAS spectra
were obtained in total-electron-yield mode with an energy
resolution of 80 meV, and the base pressure was about 1.1 ×
10−8 Pa. The HAXPES measurements were performed at
BL19LXU of SPring-8 [29], where a MBS A1-HE hemispher-

FIG. 2. Circularly polarized XAS spectra of CeCu2 Ge2 at the Ce
M4,5 absorption edges (top) obtained for x-ray incidence angles ofθ = 0◦ (μ⊥c ) and 54.7◦ (μiso ) with respect to the c axis parallel to thesurface normal. The spectral simulations assuming the ground stateof 7 (α 2 = 0.45), 7 (α 2 = 0.81), and 6 symmetry together with
the initial-state 4f charge distributions. The μ⊥c − μiso spectrum iscompared with the best-fit simulation assuming 7 ground states with
α 2 = 0.45 (bottom). The error bar of the experimental μ⊥c − μiso
spectrum is within the size of the markers.

ical electron analyzer and transmission-type phase retarders
were installed [30]. The degree of linear polarization (PL )of the polarization-switched x ray was estimated as −0.93,
corresponding to the vertically linear polarization componentsof 96.5%. The energy resolution was set to 500 meV, andthe base pressure was 1.8 × 10−7 Pa. The samples werecleaved to expose clean (001) surfaces and the measurement
temperatures were set to 6 and 10 K for XAS and HAXPES
measurements, respectively, both of which were sufficiently
lower than the excited states at ∼200 K [31].
The XAS and HAXPES spectra were simulated by making use of full multiplet calculations for Ce3+ 3d 10 4f 1 →3d 9 4f 2 and 3d 10 4f 1 → 3d 9 4f 1 + e− electric-dipole transitions, respectively, with the XTLS 9.0 program [32]. The
atomic parameters of the 4f -4f and 3d-4f Coulomb interactions, the 3d and 4f spin-orbit couplings, were obtained
from the Hartree-Fock values for Ce3+ [33]. We obtained
a reduction factor of 58% (97% and 75%) for the 4f -4f
interaction (spin-orbit couplings for 3d and 4f ) by fitting our
experimental isotropic Ce M4,5 XAS spectrum [15]. The CEF
energy for the first (second) excited states E1 (E2 ) = 197(212) K have been obtained from inelastic neutron scattering(INS) measurements [31].

121113-2

REVISING THE 4f SYMMETRY IN CeCu2 Ge2 : …

PHYSICAL REVIEW B 98, 121113(R) (2018)
(a)

(b)

FIG. 3. Anisotropic magnetic susceptibility obtained by applying a magnetic field parallel to the a and c axes. The verticaldashed line indicates TN . The inset shows the inverse magnetic
susceptibility with those obtained by simulation based on the CEF
model (solid lines). An anisotropic molecular field parameter of
λa (λc ) = −50 (0) mol/emu is taken into account in the simulation
along the a (c) axis.

Figure 2 shows the circularly polarized Ce M4,5 XAS dataof CeCu2 Ge2 (top) measured for photon incidence angles ofθ = 0◦ and 54.7◦ relative to the c axis (surface normal). The
θ = 0◦ geometry yields the XAS intensity with the linear
polarization E perpendicular to the tetragonal c axis, labeled
as μ⊥c , since the electric field vector E must be transverseto the direction of light propagation [34]. The spectrum forθ = 54.7◦ provides the polarization-averaged isotropic XAS
spectrum μiso = (2μ⊥c + μ c )/3, where μ c denotes the XAS
intensity with E parallel to the c axis. The initial-state 4f 0
components at around 888 eV are negligibly small, indicatinga highly localized character of the 4f states [18,34]. The μ⊥csignals deviate from the isotropic spectrum, as shown in the
difference spectrum defined as μ⊥c − μiso (bottom), reflecting
the orbital anisotropy of the Ce 4f states.
√ The spectral simulation rules out the |7  = α |± 25  ± 1 − α 2 |∓ 23  groundstates with α 2 = 0.81, since the polarization dependence ofthe simulated spectra at M4,5 edges is too large to accountfor the experimental data. By fitting the μ⊥c − μiso spectrum(bottom), we find the best-fit parameter of α 2 = 0.45 ± 0.05
for the 7 states, yielding a magnetic moment along the aaxis (Ma ) of 0.95μB /Ce as obtained from Fig. 1(a). Thisvalue agrees well with the in-plane Ce moment of 1.04μB as
reported in INS measurements [9,21,23]. Note that a spectral
simulation for 6 ground states results in the relative intensityof two multiplet peaks at the M5 edge different from theexperimental signals and thus the possibility of the 6 groundstates is excluded.
Figure 3 displays the magnetic susceptibility obtained under an external magnetic field of H = 5 kOe parallel to the aand c axes. In the antiferromagnetically ordered phase below
TN , the c-axis susceptibility χc is nearly constant, while the aaxis susceptibility χa tends to decrease with temperature. Thisis consistent with the ordered magnetic moment aligned in theab plane as reported in neutron measurements [23], although0

FIG. 4. (a) Ce 3d core-level spectrum together with Cu 2p states.
(b) Polarized Ce 3d5/2 HAXPES (solid lines) with the backgrounds(dashed line) obtained by the experimental geometry as shown in
Fig. 1(b). The thin and thick solid lines denote the photoelectron
intensities of Is and Ip , and corresponding LD is plotted in thebottom. The inset shows an enlarged view around the main 3d5/2
peak.

χa is smaller than χc . As shown in the inset, χc−1 is well−1
reproduced by the simulation of χCEF
given by a standard CEF
calculation assuming the 7 ground states with α 2 = 0.45 asdetermined by XAS and the CEF energy of E1 (E2 ) = 197(212) K [31]. On the other hand, χa−1 is fitted by using−1χ −1 = χCEF
− λa , where λa is the anisotropic molecular fieldparameter along the a axis of −50 mol/emu. This suggeststhat anisotropy of the magnetic exchange interactions between
the Ce ions is important for the antiferromagnetic structure.
To determine the rotational symmetry of the 7 groundstate, we have performed the Ce 3d core-level HAXPES
measurements. Figure 4(a) shows an overview of the Ce 3d
and Cu 2p core-level spectra. The Ce 3d spectrum shows
atomiclike multiplets mainly due to the 3d 9 4f 1 and 3d 9 4f 2
final states [35]. The Cu 2p spectrum shows sharp peaks without satellite 2p5 3d 9 final-state multiplet structures [36,37],
indicating that the Cu 3d states are fully occupied. Thus
the Cu 3d states hardly hybridize with the Ce 4f states.
Figure 4(b) shows the Ce 3d5/2 spectra obtained by using
linearly polarized x rays. As shown in the inset, the intensity
obtained with s- and p-polarized configurations labeled as
Is and Ip is switched around the peak top at ∼884 eV. Thisis highlighted in the linear dichroism (LD) spectrum defined
here by the difference of intensity normalized from 871.4 to121113-3

H. ARATANI et al.

PHYSICAL REVIEW B 98, 121113(R) (2018)

(c)

0
(a)

(b)
c

a
a

0

c

a
a

0

FIG. 5. (a), (b) Linearly polarized Ce 3d5/2 core-level HAXPES spectra recorded by s- and p-polarized photons together with the spectral
simulations assuming the -type 7 and -type 7 ground states for the φ = 0◦ and 45◦ configurations. The experimental geometries areillustrated on the top, where the angle between the c axis and the detected photoelectron direction is set to 55◦ . (c) φ-dependent LD obtained
by HAXPES and spectral simulations. The error bar of experimental LD spectra is indicated by the size of the markers.

841.6 eV as Is − Ip , after subtracting the background. The
sign change of the LD spectrum is attributed to the anisotropic
charge distribution of the 4f states.
Figures 5(a) and 5(b) show the experimentally observed
azimuthal rotation dependence of Ce 3d5/2 spectra (top) obtained at φ = 0◦ and 45◦ , respectively. Although the difference between Is and Ip at the higher-energy side of the peak
top is similar to each configuration, the dichroism at thelow-energy tail around 882 eV in the φ = 0◦ configurationis slightly stronger than that in the φ = 45◦ spectrum. Thistendency is clearly observed in the azimuthal angle dependence of the LD spectra as shown in Fig. 5(c). The majordifference between φ = 0◦ and 45◦ configurations is observedin the region with a positive sign of LD spectra between 880
and 883.5 eV, and the positive peak indicated by the arrowof the 45◦ spectrum is located at the higher-energy side thanthat of the φ = 0◦ spectrum. Azimuthal dependence of the
LD spectra is clearly reproduced by the spectral simulation
assuming the -type 7 ground states with the same mixing
parameter as that obtained by the XAS. Note that -type
symmetry is obviously ruled out since the spectral simulationshows the opposite trend around 882 eV for the experimental
LD spectra. Thus we can identify the in-plane rotational
symmetry of -type 7 , which is in line with the results of
NIXS measurements [19].
The 4f symmetry of CEF ground states of the Ce3+ ion in
CeCu2 Ge2 is thus successfully determined as|-type 7  =

√

  √
 
0.45 ± 25 − 0.55 ∓ 23 .

The in-plane symmetry of CeCu2 Ge2 is the same as thatofwhich has been reported as |-type 7  =√ CeCu25Si2 , √0.77 |± 2  − 0.23 |∓ 23  [18,38]. Note that the 4f charge

distribution of CeCu2 Si2 is rather compressed along the c axis
in comparison with that of CeCu2 Ge2 . Our findings suggestthat the c-axis anisotropy of the 4f states could play animportant role in emerging unconventional superconductivity. Most interesting is that the c-axis anisotropy of
CeCu2 X2 (X = Si, Ge) shows a trend opposite to that of
CeIr 1−x Rhx In5 [17], where the 4f charge distribution in
the superconducting phase expands to the c axis to gain
the hybridization with conduction electrons [17]. Therefore,
it would be important to take into account the anisotropic
hybridization effects, which induce the momentum-dependent
heavy electronic structures as reported in the superconductor CeNi2 Ge2 [39]. This motivates us the systematicinvestigation of 4f symmetry for the CeM2 X2 (M =transition metal) systems to reveal the origin of the quantum
criticality.
In conclusion, we have determined the Ce 4f symmetry of
CeCu2 Ge2 using the combined technique of polarized XAS
and core-level HAXPES. The revised out-of-plane anisotropy
parameter of α 2 was estimated as 0.45 ± 0.05, which can
explain the magnetic properties. The in-plane 4f symmetryis  type, the same as that of the superconducting CeCu2 Si2 ,suggesting that the out-of-plane anisotropy plays an essential role in driving the system into the superconducting
phase.
We acknowledge S. Takano, K. Nakagawa, M. Murata, and A. Amina for supporting HAXPES measurements.
We also thank the support of Y. Takeda of JAEA during
the beamtime. The measurements were performed under
the approval of BL23SU (Proposals No. 2013B3882, No.
2014B3882, and No. 2016A3832), and BL19LXU (Proposals No. 2014B1305 and No. 2015A1533) at SPring-8. This

121113-4

REVISING THE 4f SYMMETRY IN CeCu2 Ge2 : …

PHYSICAL REVIEW B 98, 121113(R) (2018)

work was partly carried out under the Visiting Researcher’s
Program of the Institute for Solid State Physics, The University of Tokyo. This work was financially supported by
Grants-in-Aid for Scientific Research on Innovative Areas(JP20102003, JP16H01074, and JP18H04317), a Grant-inAid for Young Scientists (JP23740240), Grant-in-Aid for

JSPS Fellows (JP16J00314 and JP16J05334), and a Grantin-Aid for Scientific Research (JP16H04014, JP18K03537,
and JP18K03512) from the Ministry of Education, Culture,
Sports, Science and Technology, Japan. Y.N. and K.Y. were
supported by the Program for Leading Graduate Schools
Interactive Materials Science Cadet Program.

[1] F. Steglich, J. Aarts, C. D. Bredl, W. Lieke, D. Meschede,
W. Franz, and H. Schäfer, Phys. Rev. Lett. 43, 1892
(1979).
[2] H. V. Löhneysen, A. Rosch, M. Vojta, and P. Wölfle, Rev. Mod.
Phys. 79, 1015 (2007).
[3] Q. Si and F. Steglich, Science 329, 1161 (2010).
[4] O. Stockert, S. Kirchner, F. Steglich, and Q. Si, J. Phys. Soc.
Jpn. 81, 011001 (2012).
[5] Z. F. Weng, M. Smidman, L. Jiao, Xin Lu, and H. Q. Yuan,
Rep. Prog. Phys. 79, 094503 (2016).
[6] K. Hagiwara, Y. Ohtsubo, M. Matsunami, S. Ideta, K. Tanaka,
H. Miyazaki, J. E. Rault, P. Le Fèvre, F. Bertran, A.
Taleb-Ibrahimi, R. Yukawa, M. Kobayashi, K. Horiba, H.
Kumigashira, K. Sumida, T. Okuda, F. Iga, and S. Kimura,Nat. Commun. 7, 12690 (2016).
[7] O. Trovarelli, M. Weiden, R. Müller-Reisener, M. GómezBerisso, P. Gegenwart, M. Deppe, C. Geibel, J. G. Sereni, and
F. Steglich, Phys. Rev. B 56, 678 (1997).
[8] H. Q. Yuan, F. M. Grosche, M. Deppe, G. Sparn, C. Geibel, and
F. Steglich, Phys. Rev. Lett. 96, 047008 (2006).
[9] F. R. de Boer, J. C. P. Klaasse, P. A. Veenhuizen, A. Bohm, C. D.
Bredl, U. Gottwick, H. M. Mayer, L. Pawlak, U. Rauschwalbe,
H. Spille, and F. Steglich, J. Magn. Magn. Mater. 63–64, 91(1987).
[10] Y. Onishi and K. Miyake, J. Phys. Soc. Jpn. 69, 3955
(2000).
[11] A. T. Holmes, D. Jaccard, and K. Miyake, J. Phys. Soc. Jpn. 76,
051002 (2007).
[12] K. Miyake and S. Watanabe, Philos. Mag. B 97, 3495 (2017).
[13] M. Smidman, D. T. Adroja, A. D. Hillier, L. C. Chapon,
J. W. Taylor, V. K. Anand, R. P. Singh, M. R. Lees, E. A.
Goremychkin, M. M. Koza, V. V. Krishnamurthy, D. M. Paul,and G. Balakrishnan, Phys. Rev. B 88, 134416 (2013).
[14] The magnetic moment is estimated as
Ma  =
ψ ∓ | g2J (J + + J − )|ψ ± , and Mc  = ψ ± |gJ Jz |ψ ±  along
the a and c axes [13], where gJ denotes a g-factor of 6/7 for a
Ce ion and the quantization axis is set to the c axis.
[15] P. Hansmann, A. Severing, Z. Hu, M. W. Haverkort, C. F.
Chang, S. Klein, A. Tanaka, H. H. Hsieh, H.-J. Lin, C. T. Chen,
B. Fåk, P. Lejay, and L. H. Tjeng, Phys. Rev. Lett. 100, 066405(2008).
[16] T. Willers, D. T. Adroja, B. D. Rainford, Z. Hu, N. Hollmann,
P. O. Körner, Y.-Y. Chin, D. Schmitz, H. H. Hsieh, H.-J. Lin,C. T. Chen, E. D. Bauer, J. L. Sarrao, K. J. McClellan, D. Byler,
C. Geibel, F. Steglich, H. Aoki, P. Lejay, A. Tanaka, L. H. Tjeng,
and A. Severing, Phys. Rev. B 85, 035117 (2012).
[17] T. Willers, F. Strigari, Z. Hu, V. Sessi, N. B. Brookes, E. D.
Bauer, J. L. Sarrao, J. D. Thompson, A. Tanaka, S. Wirth, L. H.
Tjeng, and A. Severing, Proc. Natl. Acad. Sci. USA 112, 2384
(2015).

[18] T. Willers, F. Strigari, N. Hiraoka, Y. Q. Cai, M. W. Haverkort,
K.-D. Tsuei, Y. F. Liao, S. Seiro, C. Geibel, F. Steglich, L. H.
Tjeng, and A. Severing, Phys. Rev. Lett. 109, 046401 (2012).
[19] J.-P. Rueff, J. M. Ablett, F. Strigari, M. Deppe, M. W. Haverkort,
L. H. Tjeng, and A. Severing, Phys. Rev. B 91, 201108(R)(2015).
[20] G. Knopp, A. Loidl, K. Knorr, L. Pawlak, M. Duczmal, R.
Caspary, U. Gottwick, H. Spille, F. Steglich, and A. P. Murani,
Z. Phys. B 77, 95 (1989).
[21] G. Knebel, C. Eggert, D. Engelmann, R. Viana, A. Krimmel, M.
Dressel, and A. Loidl, Phys. Rev. B 53, 11586 (1996).
[22] A. Krimmel, A. Loidl, H. Schober, and P. C. Canfield,
Phys. Rev. B 55, 6416 (1997).
[23] D. K. Singh, A. Thamizhavel, J. W. Lynn, S. Dhar, J. RodriguezRivera, and T. Herman, Sci. Rep. 1, 117 (2011).
[24] T. Mori, S. Kitayama, Y. Kanai, S. Naimen, H. Fujiwara, A.
Higashiya, K. Tamasaku, A. Tanaka, K. Terashima, S. Imada,
A. Yasui, Y. Saitoh, K. Yamagami, K. Yano, T. Matsumoto, T.
Kiss, M. Yabashi, T. Ishikawa, S. Suga, Y. Ōnuki, T. Ebihara,
and A. Sekiyama, J. Phys. Soc. Jpn. 83, 123702 (2014).
[25] Y. Kanai, T. Mori, S. Naimen, K. Yamagami, H. Fujiwara,
A. Higashiya, T. Kadono, S. Imada, T. Kiss, A. Tanaka, K.
Tamasaku, M. Yabashi, T. Ishikawa, F. Iga, and A. Sekiyama,
J. Phys. Soc. Jpn. 84, 073705 (2015).
[26] S. Hamamoto, S. Fujioka, Y. Kanai, K. Yamagami, Y. Nakatani,
K. Nakagawa, H. Fujiwara, T. Kiss, A. Higashiya, A. Yamasaki,
T. Kadono, S. Imada, A. Tanaka, K. Tamasaku, M. Yabashi, T.
Ishikawa, K. T. Matsumoto, T. Onimaru, T. Takabatake, and A.
Sekiyama, J. Phys. Soc. Jpn. 86, 123703 (2017).
[27] B. Zeng, Q. R. Zhang, D. Rhodes, Y. Shimura, D. Watanabe,
R. E. Baumbach, P. Schlottmann, and T. Ebihara, and L. Balicas
Phys. Rev. B 90, 155101 (2014).
[28] Y. Saitoh, Y. Fukuda, Y. Takeda, H. Yamagami, S. Takahashi,
Y. Asano, T. Hara, K. Shirasawa, M. Takeuchi, T. Tanaka, andH. Kitamura, J. Synchrotron Radiat. 19, 388 (2012).
[29] M. Yabashi, K. Tamasaku, and T. Ishikawa, Phys. Rev. Lett. 87,
140801 (2001).
[30] H. Fujiwara, S. Naimen, A. Higashiya, Y. Kanai, H. Yomosa,K. Yamagami, T. Kiss, T. Kadono, S. Imada, A. Yamasaki,
K. Takase, S. Otsuka, T. Shimizu, S. Shingubara, S. Suga,
M. Yabashi, K. Tamasaku, T. Ishikawa, and A. Sekiyama,
J. Synchrotron Radiat. 23, 735 (2016).
[31] M. Loewenhaupt, E. Faulhaber, A. Schneidewind, M. Deppe,and K. Hradil, J. Appl. Phys. 111, 07E124 (2012).
[32] A. Tanaka and T. Jo, J. Phys. Soc. Jpn. 63, 2788 (1994).
[33] B. T. Thole, G. van der Laan, J. C. Fuggle, G. A. Sawatzky,
R. C. Karnatak, and J.-M. Esteva, Phys. Rev. B 32, 5107
(1985).
[34] Y. Saitoh, H. Fujiwara, T. Yamaguchi, Y. Nakatani, T. Mori,
H. Fuchimoto, T. Kiss, A. Yasui, J. Miyawaki, S. Imada, H.

121113-5

H. ARATANI et al.

PHYSICAL REVIEW B 98, 121113(R) (2018)

Yamagami, T. Ebihara, and A. Sekiyama, J. Phys. Soc. Jpn. 85,
114713 (2016).
[35] M. Yano, A. Sekiyama, H. Fujiwara, Y. Amano, S. Imada, T.
Muro, M. Yabashi, K. Tamasaku, A. Higashiya, T. Ishikawa, Y.
Ōnuki, and S. Suga, Phys. Rev. B 77, 035118 (2008).
[36] Z.-X. Shen, J. W. Allen, J. J. Yeh, J.-S. Kang, W. Ellis, W.
Spicer, I. Lindau, M. B. Maple, Y. D. Dalichaouch, M. S.
Torikachvili, J. Z. Sun, and T. H. Geballe, Phys. Rev. B 36, 8414
(1987).

[37] J. Ghijsen, L. H. Tjeng, J. van Elp, H. Eskes, J. Westerink, G. A.
Sawatzky, and M. T. Czyzyk, Phys. Rev. B 38, 11322 (1988).
[38] E. A. Goremychkin and R. Osborn, Phys. Rev. B 47, 14280(1993).
[39] Y. Nakatani, H. Aratani, H. Fujiwara, T. Mori, A. Tsuruta, S. Tachibana, T. Yamaguchi, T. Kiss, A. Yamasaki,
A. Yasui, H. Yamagami, J. Miyawaki, T. Ebihara, Y.
Saitoh, and A. Sekiyama, Phys. Rev. B 97, 115160(2018).

121113-6