Magnetic and 151Eu M?ssbauer spectroscopic studies on rare earth bismuth sulfides, EuLnBiS4 (Ln = Eu, Gd)

Article abstract of DOI:10.1016/j.jssc.2018.05.006

Ternary and quaternary rare earth bismuth sulfides EuLnBiS₄ (Ln = Eu, Gd) have been investigated by X-ray diffraction, ¹⁵¹Eu M?ssbauer spectroscopy, and magnetic susceptibility measurements. Both compounds have the orthorhombic CaFe<

Full text of DOI:10.1016/j.jssc.2018.05.006

Journal of Solid State Chemistry 264 (2018) 108–112
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Magnetic and 151Eu Mössbauer spectroscopic studies on rare earth bismuth
sulfides, EuLnBiS4 (Ln = Eu, Gd)
Makoto Wakeshima, Yukio Hinatsu⁎
Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060 – 0810, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords:
Ternary and quaternary rare earth bismuth sulfides EuLnBiS4 (Ln = Eu, Gd) have been investigated by X-ray
diffraction, 151Eu Mössbauer spectroscopy, and magnetic susceptibility measurements. Both compounds have
the orthorhombic CaFe2O4-type structure with space group Pnma. In Eu2BiS4, Eu2+ and Eu3+ ions occupy two
crystallographically independent sites. The 151Eu Mössbauer spectra for Eu2BiS4 indicate that the Eu2+ and
Eu3+ ions exist in the molar ratio of 1:1, and the Debye temperatures of Eu2+ and Eu3+ are 175 and 230 K,
respectively. Magnetic susceptibility measurements for Eu2BiS4 and EuGdBiS4 reveal that an antiferromagnetic
transition occurs at 2.8 and 6.5 K, respectively.
151Eu Mössbauer spectrum
Rare earth
Sulfide
Magnetic properties
1. Introduction
of the above-mentioned sulfides and is similar to that for Eu2CuS3 [13],
i.e., Eu2BiS4 has two crystallographically distinguishable sites for Eu2+
It is well known that mixed-valence europium sulfides show an
interesting electronic and magnetic behavior. For example, Eu3S4 has
the Verwey transition at 186 K [1] and the ferromagnetic transition at
and Eu3+ ions. However, none of the studies on the electronic and
magnetic properties for this mixed valence compound has been carried
out.
In this study, two polycrystalline samples of EuLnBiS4 (Ln = Eu,
Gd) were prepared. Their magnetic susceptibilities were measured in
the temperature range from 1.8 to 300 K and 151Eu Mössbauer
spectrum measurements were performed from 20 to 300 K.
3.1 K [2]. EuPd3S4 shows an electron hopping between Eu2+ and Eu3+
,
and has the antiferromagnetic transition at 3 K [3]. Similar electron
hopping between Eu2+ and Eu3+ has been observed in Eu5Zr3S12 [4],
Na1.515EuGeS4 [5], and (EuS)1.173NbS2 [6]. Eu5Sn3S12 is metamagnetic
and has two field-dependent antiferromagnetic phases at low tempera-
tures [7–9].
2. Experimental
In these compounds, the europium ions have two oxidation states.
In general, the divalent state of Eu is stable in sulfides, but some
compounds contain trivalent europium. Flahaut noted that they are
classified into two types [10]. In the case of compounds containing only
Eu3+ ions, there is necessarily a strongly electronegative anion, or a
second weakly electronegative cation. For compounds containing both
Eu2+ and Eu3+, such as Eu3S4 and EuPd3S4, 151Eu Mössbauer spectro-
scopic measurements were performed to investigate the mixed-valence
state of Eu [3,11]. These compounds show the occurrence of the
2.1. Sample preparation
Two europium bismuth sulfides, Eu2BiS4 and EuGdBiS4, were
prepared by the solid-state reaction. As starting materials, rare earth
sesquioxides (Eu2O3, Gd2O3), powder sulfur (S), and powered Bi
metals were used. Europium monosulfide EuS was prepared by heating
europium sesquioxide (Eu2O3) on a graphite boat at 1073 K for 10 h in
a flowing gaseous CS2 by bubbling the nitrogen gas through liquid CS2.
Eu3S4 was prepared by heating stoichiometric mixtures of EuS and S
powders in a quartz ampoule at 1073 K for 24 h. Gadolinium sesqui-
sulfide (Gd2S3) was obtained by heating Gd2O3 in a flowing atmosphere
of CS2 gas at 1473 K for 2 h. Bismuth sesquisulfide (Bi2S3) was
prepared by heating stoichiometric amounts of Bi and S powders at
823 K for 6 h. Then, stoichiometric mixtures of Eu3S4, Gd2S3, and Bi2S3
were intimately ground and pressed into pellets. They were heated in a
quartz ampoule at 1223 K for 12 h.
electron transfer and/or the electron hopping between Eu2+ and Eu3+
which may stabilize the Eu3+ ions.
,
Ternary europium bismuth sulfide Eu2BiS4 has been reported to
crystallize in the orthorhombic CaFe2O4-type structure with space
group Pnma [12]. The schematic structure of Eu2BiS4 is illustrated in
Fig. 1. This compound has the formal oxidation state of
Eu2+Eu3+Bi3+S2–4, and the Eu2+ and Eu3+ ions occupy crystallographi-
cally different sites. The situation for Eu2BiS4 is different from the case
⁎
Corresponding author.
E-mail address: hinatsu@sci.hokudai.ac.jp (Y. Hinatsu).
https://doi.org/10.1016/j.jssc.2018.05.006
Received 22 March 2018; Received in revised form 1 May 2018; Accepted 6 May 2018
Available online 09 May 2018
0022-4596/ © 2018 Elsevier Inc. All rights reserved.

M. Wakeshima, Y. Hinatsu
Journal of Solid State Chemistry 264 (2018) 108–112
Fig. 2. Powder x-ray diffraction patterns and Rietveld refinements for (a) Eu2BiS4 and
(b) EuGdBiS4. The bottom trace is a plot of the difference between observed + (cross
makers) and calculated (solid line) intensities. All allowed Bragg reflections are shown by
vertical lines.
Fig. 1. Crystal structure of Eu2BiS4.
3. Results and discussion
2.2. Powder X-ray diffraction
3.1. Structures of Eu2BiS4 and EuGdBiS4
Powder X-ray diffraction profiles were measured using a Rigaku
Multi-Flex diffractometer with Cu-Kα radiation equipped with a curved
graphite monochromator. The data were collected by step-scanning in
the angle range of 10° ≤ 2θ ≤ 120° at a 2θ step-size of 0.02°. The X-ray
diffraction data were analyzed by the Rietveld technique, using the
program RIETAN-FP [14] and the crystal structure was drawn by
VESTA program [15].
Both the Eu2BiS4 and EuGdBiS4 compounds were obtained as a
single phase. The X-ray diffraction profiles were indexed on an
orthorhombic cell with the space group Pnma, and their crystal-
lographic parameters were refined by the RIETAN-FP program.
Fig. 2(a) and (b) show the X-ray diffraction profiles of Eu2BiS4 and
EuGdBiS4, respectively. The calculated profiles are in good agreements
with the observed ones (Eu2BiS4: Rwp = 8.49%, RI = 2.08%; EuGdBiS4:
Rwp = 7.13%, RI = 1.84%). The refined lattice parameters and
positional parameters for Eu2BiS4 and EuGdBiS4 are listed in
Table 1. From the X-ray diffraction profile for EuGdBiS4, the crystal-
lographic site of Gd3+ cannot be distinguished from that of Eu2+
because these ions have the same number of electrons. However, on the
assumption that the divalent Eu and trivalent Gd sites in the EuGdBiS4
correspond to the the Eu(1) and Eu(2) sites in the Eu2BiS4, respec-
tively, the positional parameters for EuGdBiS4 should be well refined,
as will be discussed later. Some selected interatomic distances for
Eu2BiS4 and EuGdBiS4 are listed in Table 2.
Fig. 3(a) and (b) illustrate the polyhedral representation of the
Eu2BiS4 structure. The Eu ions occupy two crystallographically in-
dependent sites. The Eu(1) and Eu(2) ions are coordinated by eight and
seven sulfide ions, respectively. The Eu(1)S8 and Eu(2)S7 polyhedra are
connected to each other by face sharing as shown in Fig. 3(a). The Bi
ions are coordinated by six sulfide ions and the BiS6 octahedra share
edges, forming double chains along the b-axis as shown in Fig. 3(b).
The valences of the cations are calculated by the bond valence sum
(Vi) [16]:
2.3. 151Eu Mössbauer spectra
The 151Eu Mössbauer spectra were measured in the temperature
range between 20 and 300 K with a Mössbauer spectrometer VT-6000
(Laboratory Equipment Co.) in the constant acceleration mode using a
radiation source 151SmF3 (1.85 GBq). The spectrometer was calibrated
with a spectrum of α-Fe at room temperature. The γ-rays were detected
with a NaI scintillation counter. Europium trifluoride (EuF3) was used
as a reference standard for the chemical isomer shift. The sample was
wrapped in an aluminum foil so as to have its average surface density of
10 mg (Eu) cm–2
.
2.4. Magnetic susceptibility
The temperature-dependence of the magnetic susceptibility was
measured in an applied field of 0.1 T over the temperature range of 1.8
⎛
⎞
R0 − dij
v = exp
,
K ≤ T ≤ 400 K, using
a
SQUID magnetometer (Quantum Design,
⎜
⎟
⎠
ij
b
⎝
(1)
(2)
MPMS5S). The susceptibility measurements were performed under
both zero-field-cooled (ZFC) and field-cooled (FC) conditions. The
former was measured upon heating the sample to 400 K under the
applied magnetic field of 0.1 T after zero-field cooling to 1.8 K. The
latter was measured upon cooling the sample from 400 to 1.8 K in the
applied field of 0.1 T.
V =
v ,
ij
∑
i
j
where R0 and b are known as the bond valence parameters of various
cations and a constant value (0.37 Å), respectively, and dij means the
109

M. Wakeshima, Y. Hinatsu
Journal of Solid State Chemistry 264 (2018) 108–112
Table 1
Lattice and positional parameters for Eu2BiS4 and EuGdBiS4.
Eu2BiS4
Space Group: Pnma (No. 62)
a = 11.5132(8) Å, b = 4.0775(3) Å, c = 14.4501(8) Å
RI = 2.08 %, Rwp = 8.49 %, S = 1.31
Site
x
y
z
B / Å2
Eu(1)
Eu(2)
Bi
S(1)
S(2)
S(3)
S(4)
4c
4c
4c
4c
4c
4c
4c
0.2698(2)
0.1126(1)
0.0650(1)
0.0121(6)
0.2628(6)
0.0495(6)
0.3235(6)
1/4
1/4
1/4
1/4
1/4
1/4
1/4
0.6537(1)
0.9050(1)
0.3905(1)
0.7169(4)
0.3050(5)
0.0898(4)
0.0121(5)
0.9(2)
0.6(3)
0.8(1)
1.1(3)
1.1*
1.1*
1.1*
EuGdBiS4
Space Group: Pnma (No. 62)
a = 11.4842(8) Å, b = 4.0730(3) Å, c = 14.4383(8) Å
RI = 1.84 %, Rwp = 7.13 %, S = 1.21
Site
x
y
z
B / Å2
Eu
Gd
Bi
S(1)
S(2)
S(3)
S(4)
4c
4c
4c
4c
4c
4c
4c
0.2707(2)
0.1114(1)
0.0642(1)
0.0127(6)
0.2665(6)
0.0502(6)
0.3262(6)
1/4
1/4
1/4
1/4
1/4
1/4
1/4
0.6539(1)
0.9040(1)
0.3901(1)
0.7164(4)
0.3048(5)
0.0906(4)
0.0117(5)
0.8(2)
0.4(2)
0.6(1)
1.0(3)
1.0*
1.0*
1.0*
*
The atomic displacement parameters of S(2), S(3), and S(4) are fixed to be that of S(1).
Table 2
Selected interatomic distances (Å) for Eu2BiS4 and EuGdBiS4.
Eu2BiS4
Eu(1)
EuGdBiS4
−S(1)
−S(1)
−S(2)
−S(3)
−S(4)
−S(1)
−S(2)
−S(3)
−S(3)
−S(4)
−S(1)
−S(2)
−S(4)
−S(4)
3.104(7)
3.359(7)
3.013(6)
3.056(5)
3.082(6)
2.955(7)
2.882(5)
2.764(5)
2.767(7)
2.879(7)
2.712(5)
2.591(7)
2.981(6)
3.116(7)
Eu
Gd
Bi
−S(1)
3.098(8)
3.351(8)
3.013(6)
3.035(6)
3.098(6)
2.936(7)
2.858(5)
2.756(5)
2.784(7)
2.916(8)
2.701(5)
2.630(7)
2.969(6)
3.079(8)
Fig. 3. Polyhedral representation of the Eu2BiS4 structure. (a) Eu(1)S8 polyhedra and
−S(1)
−S(2)
−S(3)
−S(4)
−S(1)
−S(2)
−S(3)
−S(3)
−S(4)
−S(1)
−S(2)
−S(4)
−S(4)
Eu(2)S7 polyhedra. (b) The double chains composed of BiS6 octahedra.
×2
×2
×2
×2
×2
×2
Eu(2)
×2
×2
×2
×2
Bi
×2
×2
×2
×2
interatomic distance between cation i and anion j. For Eu2BiS4, the
valences of the Eu(1), Eu(2), and Bi ions were determined to be +1.90,
+3.55, and +3.19, respectively, which indicates that the divalent and
trivalent europium ions occupy the Eu(1) and Eu(2) sites, respectively.
The large value of V(Eu3+) suggests that the site of Eu(2) is too small
for Eu3+ ion. Due to this, the synthesis of EuLnBiS4 containing a larger
trivalent Ln ions than Eu3+ was unsuccessful. For EuGdBiS4, the
valences of the Eu(1), Gd, and Bi ions were calculated to be +1.92,
+3.10, and +3.19, respectively.
Fig. 4. 151Eu Mössbauer spectra of Eu2BiS4 at room temperature. The top trace is a plot
of the difference between observed
○ (circle makers) and calculated (solid line)
transmissions.
absorption peak should be fitted with twelve Lorentzian lines. To
simplify this analysis, each peak was fitted with a single Lorentzian.
The isomer shifts (δ) relative to EuF3 are obtained to be –12.23(2) mm
s–1 for Eu2+ and 0.74(2) mm s–1 for Eu3+, and these values are nearly
equal to those for Eu2+ and Eu3+ in other sulfides. The ratio of the
absorption intensities for Eu2+ and Eu3+ is calculated to be 0.7: 1.0. On
the other hand, the results of the X-ray diffraction measurements at
room temperature showed that the ratio of Eu2+ and Eu3+ is 1: 1.
In order to elucidate the difference in the ratio of Eu2+ and Eu3+
3.2. 151Eu Mössbauer spectra
Fig. 4 shows the 151Eu Mössbauer spectrum of Eu2BiS4 measured at
room temperature. Two absorption peaks appear at −12.2 mm s−1 and
0.7 mm s−1, indicating the presence of the divalent and trivalent Eu
ions in this compound. Since both the Eu sites in Eu2BiS4 have the low
point symmetry (see Table 2), an electric field gradient (EFG) tensor
exists. Due to the distortion by the quadrupole interaction, each
110

M. Wakeshima, Y. Hinatsu
Journal of Solid State Chemistry 264 (2018) 108–112
Fig. 7. Temperature dependence of the isomer shifts (δ) for Eu2+ and Eu3+ in Eu2BiS4.
The dotted line is the theoretical curve of the second-order Doppler (SOD) shift with ΘD
= 230 K and the broken line is that of the SOD shift with ΘD = 175 K.
Fig. 5. 151Eu Mössbauer spectra of Eu2BiS4 measured at 20, 100, 200, and 300 K.
Fig. 6. Temperature dependence of the absorption area of intensities for Eu2+ and Eu3+
in Eu2BiS4. The solid line is the theoretical curve (ΘD = 230 K) normalized to A(Eu3+) at
20 K and the broken line is the theoretical curve (ΘD = 175 K) normalized to A(Eu2+) at
20 K.
between the X-ray diffraction and the 151Eu Mössbauer spectrum
measurements, low temperature 151Eu Mössbauer spectrum measure-
ments were performed down to 20 K. Fig. 5 shows the 151Eu Mössbauer
spectra of Eu2BiS4 between 20 and 300 K. The absorptions of Eu2+ (δ ~
−12.2 mm s–1) and Eu3+ (δ ~ 0.8 mm s–1) are observed at all tempera-
tures.
Fig. 6 shows the temperature dependences of the absorption area of
the intensities for Eu2+ and Eu3+ in Eu2BiS4. Both the intensities
decrease monotonously with increasing temperature and the decrease
for Eu2+ is larger than that for Eu3+. At 20 K, the intensities for Eu2+
and Eu3+ are almost equal, but the ratio of the intensities for Eu2+ and
Eu3+ is found to be 0.7: 1 at 300 K. This variation of the intensity with
Fig. 8. Temperature dependence of the reciprocal magnetic susceptibility (χ−1) of (a)
Eu2BiS4 and (b) EuGdBiS4 measured in the magnetic field of 0.1 T. A solid line is the
fitting result by the Curie-Weiss law. The insets show the low-temperature dependence of
susceptibility of (a) Eu2BiS4 and (b) EuGdBiS4.
111

M. Wakeshima, Y. Hinatsu
Journal of Solid State Chemistry 264 (2018) 108–112
Table 3
magnetic moment is calculated to be 7.94 μB from the relation μeff = gJ
J(J + 1) (gJ is the Lande g-factor, and J is the total angular
momentum). For the Eu3+ ion, the ground state is 7F0, which means
that its contribution to the magnetic moment of Eu2BiS4 is negligible.
Therefore, the effective magnetic moment for Eu2BiS4 should be 7.94
μB. The moment obtained from magnetic susceptibility measurements
is in accordance with this value.
The effective magnetic moments (μeff: experimental, μcalc: calculated) per formula unit,
Weiss constants, and Neel temperature for Eu2BiS4 and EuGdBiS4.
μeff / μB
μcalc / μB
θ / K
ΤΝ / K
Eu2BiS4
EuGdBiS4
7.93(2)
11.13(1)
7.94
11.23
2.7(1)
–0.9(1)
2.8
6.5
The values of μeff and ΘW for EuGdBiS4 have been determined to be
11.13 μB and −0.92 K, respectively. Both the Eu2+ and Gd3+ contribute
to the magnetic properties of EuGdBiS4. These ions have the same
electron configuration ([Xe]4f7) and the same ground state (8S7/2).
Therefore, the effective magnetic moment of EuGdBiS4 is calculated to
temperature may be due to a small difference in the Debye-Waller
factors between Eu2+ and Eu3+. The area of the intensity is propor-
tional to the recoil-free fraction. On the assumption that the valence
fluctuation does not occur below 300 K, the Debye temperatures (ΘD)
for Eu2+ and Eu3+ are estimated from the recoil-free fraction (f). The
recoil-free fraction is represented by the following equation [17],
2
2
be μeff
=
μEu
+ μGd
= 11.23 μB. The experimental magnetic
2+
3+
moment is in good agreement with this theoretical moment.
The magnetic susceptibilities (χ) for Eu2BiS4 in the lower tempera-
ture region are shown in the inset of Fig. 8(a). It is found that Eu2BiS4
shows an antiferromagnetic transition at 2.8 K. No divergence between
the ZFC and FC magnetic susceptibility is observed. For EuGdBiS4,
magnetic susceptibility measurements show the occurrence of an
antiferromagnetic ordering without ferromagnetic component below
6.5 K (see the inset of Fig. 8(b)). It is considered that the substitution of
the magnetic Gd3+ ion (8S7/2) for the nonmagnetic Eu3+ ion (7F0)
causes the higher Néel temperature for EuGdBiS4.
⎡
⎢
2
⎤
⎧
⎪
⎫
⎪
⎛
⎜
⎝
⎞
⎟
⎠
Θ /T
D
−6ER
kBΘD
1
4
T
D
xdx
⎥
⎨
⎪
⎩
⎬
⎪
⎭
f = exp
+
,
∫
Θ
0
(ex − 1)
⎢
⎥
⎣
⎦
(3)
where kB is the Boltzmann's constant and ER is the free-atom recoil
energy. The theoretical curves with ΘD = 175 K (broken line in Fig. 6)
and ΘD = 230 K (solid line in Fig. 6) using this equation are in good
agreement with the experimental data for Eu2+ and Eu3+, respectively.
The higher Debye temperature for the Eu3+ ion indicates that the
Eu3+−S2− bonds in the Eu(2)S7 polyhedron are stronger than the
Eu2+−S2− bonds in the Eu(1)S8 polyhedron.
Acknowledgements
Fig. 7 shows the temperature dependence of isomer shifts (δ) for
Eu2+ and Eu3+. Both the isomer shifts decrease with increasing
temperature, which is attributable to the effects of the second-order
Doppler shifts [17]. However, the difference in the isomer shifts
between Eu2+ and Eu3+ is invariable against temperature. This result
is contrastive to the result observed in the 151Eu Mössbauer spectra for
some mixed-valence europium sulfides such as Eu3S4, EuPd3S4,
Eu5Zr3S12, Na1.515EuGeS4, and (EuS)1.173NbS2 [3–6,11]. In these
compounds, the spectra consist of two absorption peaks for Eu2+ and
Eu3+ at low temperatures. With increasing temperatures, the two peaks
become wider and approach each other, and only one broad peak is
observed at room temperature, which is due to the electron hopping
between Eu2+ and Eu3+. Therefore, our experimental results show that
such an electron hopping does not occur in the present sulfide Eu2BiS4.
This study was partly supported by Advanced Physical Property
Open Unit (APPOU), Hokkaido University.
References
[1] R. Pott, G. Guntherodt, Phys. Rev. B 27 (1983) 359–363.
[2] O. Massenet, J.M.D. Coey, J. Phys. Colloq. 37 (C4) (1976) 297–300.
[3] M. Wakeshima, Y. Hinatsu, J. Solid State Chem. 157 (2001) 117–122.
[4] P. Jakubcova, F.M. Schappacher, R. Pöttgen, D. Johrendt, Z. Anorg. Allg. Chem.
635 (2009) 759–763.
[5] A. Choudhury, F. Grandjean, G.J. Long, P.K. Dorhout, Inorg. Chem. 51 (2012)
11779–11786.
[6] L. Cario, P. Palvadeau, A. Lafond, C. Deudon, Y. Moëlo, B. Corraze, A. Meerschaut,
Chem. Mater. 15 (2003) 943–950.
[7] T.I. Volkonskaya, A.G. Gorobets, S.A. Kizhaev, I.A. Smirnov, V.V. Tikhonov,
M. Guittard, C. Lavenant, J. Flahaut, Phys. Status Solidi (a) 57 (1980) 731–734.
[8] S. Jaulmes, M. Julien-Pouzol, Acta Crystallogr. B33 (1977) 1191–1193.
[9] P. Jakubcova, D. Johrendt, C.P. Sebastian, S. Rayaprol, R. Pöttgen, Z. Naturforsch,
Sect. B-A J. Chem. Sci. 62 (2007) 5–14.
3.3. Magnetic properties
[10] K.A. Gschneidner, Jr.L. Eyring (Eds.), Handbook on the Physics and Chemistry of
Rare Earth, North-Holland Publishing Company, 1979.
[11] B.C. Bunker, R.S. Drago, M.K. Kroeger, J. Am. Chem. Soc. 104 (1982) 4593–4598.
[12] P. Lemoine, D. Carre, M. Guittard, Acta Crystallogr. B38 (1982) 727–729.
[13] F. Furuuchi, M. Wakeshima, Y. Hinatsu, J. Solid State Chem. 177 (2004)
3853–3858.
[14] F. Izumi, K. Momma, Solid State Phenom. 130 (2007) 15–20.
[15] K. Momma, F. Izumi, Appl. Crystallogr. 41 (2008) 653–658.
[16] N.E. Brese, M. O’Keeffe, Acta Crystallogr B47 (1991) 192–197.
[17] N.N. Greenwood, T.C. Gibb, Mössbauer Spectroscopy, Plenum, New York, 1971.
Fig. 8(a) and (b) show the temperature dependence of reciprocal
magnetic susceptibilities (χ −1) for Eu2BiS4 and EuGdBiS4, respec-
tively. Both the magnetic susceptibilities follow the Curie-Weiss law
in the temperature range between 50 and 300 K. Table 3 lists the
effective magnetic moment (μeff) and the Weiss constant (ΘW) for
Eu2BiS4 and EuGdBiS4. In the Eu2BiS4, both the europium ions, Eu2+
and Eu3+ contribute to its magnetic properties. The electron config-
uration of Eu2+ is [Xe]4f7 ([Xe]: core electron configuration of xenon)
8
and the ground state of the Eu2+ ion is S7/2. Therefore, the effective
112