Thermodynamic properties and rare-earth spectroscopy of Cu3Nd(SeO3)2O2X (X = Cl, Br)

Article abstract of DOI:10.1016/j.jmmm.2019.165721

The kagome lattice of copper ions in francisite-type compounds is quite sensitive to external stimuli, being easily affected by temperature and magnetic field. The rare-earth ions inserted between buckled layers of transition metal add new dimension to ma

Full text of DOI:10.1016/j.jmmm.2019.165721

Journal Pre-proofs
Thermodynamic properties and rare-earth spectroscopy of Cu3Nd(SeO3)2O2X
(X = Cl, Br)
Maria M. Markina, Konstantin V. Zakharov, Peter S. Berdonosov, Valery A.
Dolgikh, Elena S. Kuznetsova, Sergei A. Klimin, Oleg B. Yumashev, Alexander
N. Vasiliev
PII:
S0304-8853(19)32132-8
DOI:
https://doi.org/10.1016/j.jmmm.2019.165721
MAGMA 165721
Reference:
Journal of Magnetism and Magnetic Materials
To appear in:
Received Date:
Accepted Date:
19 June 2019
18 August 2019
Please cite this article as: M.M. Markina, K.V. Zakharov, P.S. Berdonosov, V.A. Dolgikh, E.S. Kuznetsova, S.A.
Klimin, O.B. Yumashev, A.N. Vasiliev, Thermodynamic properties and rare-earth spectroscopy of
Cu3Nd(SeO3)2O2X (X = Cl, Br), Journal of Magnetism and Magnetic Materials (2019), doi: https://doi.org/10.1016/
j.jmmm.2019.165721
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Thermodynamic properties and rare-earth
spectroscopy of Cu3Nd(SeO3)2O2X (X = Cl, Br)
Maria M. Markina,1 Konstantin V. Zakharov,1 Peter S. Berdonosov,1 Valery A. Dolgikh,1 Elena
S. Kuznetsova,1 Sergei A. Klimin,2 Oleg B. Yumashev,3 Alexander N. Vasiliev1,4,5*
1Lomonosov Moscow State University, Moscow 119991, Russia
2Institute of Spectroscopy, RAS, Troitsk 142190, Russia
3Institute of Applied Mechanics, RAS, Moscow 125040, Russia
4National University of Science and Technology “MISiS”, Moscow 119049, Russia
5National Research South Ural State University, Chelyabinsk 454080, Russia
KEYWORDS francisite, metamagnetic phase transition, kagome lattice, magnetic phase
diagram, rare-earth spectroscopy.
The kagome lattice of copper ions in francisite-type compounds is quite sensitive to external
stimuli, being easily affected by temperature and magnetic field. The rare-earth ions inserted
between buckled layers of transition metal add new dimension to magnetism in these systems.
*vasil@mig.phys.msu.ru, +7(495)932-92-17
1

Neodymium francisites, Cu3Nd(SeO3)2O2X (X = Cl, Br), experience long range magnetic order at
TN = 34 K (Cl) or 35.2 K (Br) and spin reorientation transition at TR = 4 K (Cl) or 4.6 K (Br)
marked by sharp anomalies in magnetization M, specific heat Cp, and optical spectra. The spin
reorientation of Cu2+ ions is due to d-f interaction of transition and rare-earth magnetic
subsystems. Under action of modest external field B < 2 T both compounds exhibit
metamagnetic phase transition, largely hysteretic in case of Cl compound at T < TR.
Introduction
Low dimensional and frustrated magnetic systems attract immense attention due to the rich
palette of ordered and disordered quantum ground states.1 Exotic phases realized at low
temperatures include gapped2 and gapless3 spin liquids, skyrmions4 and Z2 vortices,5 non-trivial
long-range ordered structures,6 etc. Among this multitude, the francisite mineral,
Cu3Bi(SeO3)2O2Cl, is notable owing to its six-sublattices non-collinear antiferromagnetic spin
arrangement. The crystal structure of natural francisite initially has been described in mineral
science.7-10 First rare-earth substituted compound, Cu3Er(SeO3)O2Cl, isostructural to the pristine
one was synthesized soon afterwards.11
Basic physical properties of synthetic Cu3Bi(SeO3)2O2X (X = Cl, Br) were established in
pioneering work of Millet et al.12 Sharp anomalies in magnetic susceptibility were detected in Cl
and Br compounds at comparable temperatures TN ~ 24 K, albeit authors claimed “...no evidence
for a magnetically ordered state at low temperatures”. Besides, additional anomalies in linear
birefringence at about TS ~ 125 K were seen in both Cl and Br species ascribed to unidentified
structural phase transition. Finally, two series of Cl and Br rare-earth francisite-type compounds
2

were systematically synthesized confirming their orthorhombic crystal structure, space group
Pmmn.13 No similar compounds with tellurium were found. Overall, about twenty five Cl and Br
francisite-type compound were reported (Cu3Bi(SeO3)2O2I unconfirmed) most being virtually
uninvestigated in physical measurements.14
Magnetic structure of Cu3Bi(SeO3)2O2Br was solved by single-crystal neutron diffraction.15
Below TN = 27.4 K, this compound is the layered antiferromagnet with six-sublattices canted
ferrimagnetic spin arrangement. The non-collinearity of Cu2+ magnetic moments stems from the
competition of multiple ferromagnetic and antiferromagnetic intralayer exchange interactions.
The response of Br francisite to external magnetic field is quite anisotropic. At magnetic field B
~ 0.8 T applied along the c axis, i.e. perpendicular to ab layers, the system experiences sharp
metamagnetic transition associated with a flip of every second magnetic layer. Much higher
fields are needed to rotate the magnetization toward the b axis (B ~ 7 T) or the a axis (B ~ 15
T).15 These observations were analyzed and confirmed in the first principles study of the
magnetic ground state of Cl and Br francisites.16 The doping of Cu3Bi(Se1-xTexO3)2O2Cl (0  x 
0.6) polycrystalline samples was undertaken to further explore the metamagnetic phase
transition.17
Further research on Cu3Bi(SeO3)2O2X (X = Cl, Br) concentrated on antiferroelectric lattice
distortion observed in Cl compound at TS = 115 K and absent in its Br counterpart down to
lowest temperatures. At phase transition, the orthorhombic space group Pmmn reduces to a lower
symmetry space group Pcmn due the doubling of unit cell along the c axis. This phase transition
was detected by high-resolution synchrotron powder diffraction,18 single crystal neutron
diffraction,19 Raman scattering20 and through measurements of various dielectric and thermal
parameters.
3

The studies of yttrium21 and “non-magnetic” rare-earth francisites based on lanthanum,22
europium and lutetium23 revealed similarity in their magnetic response to bismuth francisite
albeit no signatures of antiferroelectric phase transition were seen in any of them. Interestingly,
the room temperature crystal structure of Te substituted francisite, Cu3Bi(TeO3)2O2Cl, is
isostructural with the low temperature phase of Cu3Bi(SeO3)2O2Cl.24
The spin-flip-induced ferroelectricity was observed in measurements of dielectric constant and
electric polarization in Cu3Bi(SeO3)2O2Cl under action of external magnetic field.25 This
observation allows attributing the francisite to highly demanded multiferroic materials. Another
practically important feature of francisite-type compounds concerns controllable broadband
absorption observed in a multifrequency electron spin resonance study on Cu3Bi(SeO3)2O2Br.26
Namely, the mixed phase stabilized in vicinity of metamagnetic transition at B = 0.8 T below TN
possesses an enhanced microwave absorption. This absorption is non-resonant showing no
frequency dependence in the range 100–480 GHz.27
New features in behavior of francisite-type compounds appear at “magnetic” rare-earth
substitution of bismuth for samarium28 and ytterbium.29 Both compounds order magnetically at TN
= 35 K (Sm) or 36.7 K (Yb), but the interplay of rare-earth and transition metal subsystems
results in spin-reorientation of Cu spins at TR ~ 9 K. The infrared spectroscopy of rare-earth ions
evidences splitting of the lowest-energy excited Kramers doublet at TR < T < TN while the ground
Kramers doublet splits only at T < TR. Preliminary data on electronic spectra of rare-earth ions in
Cu3R(SeO3)2O2Cl (R = Sm, Yb, Er, Nd, Pr, Eu) represent the phase transitions being detected
either by splitting of crystal-field doublets or by repulsion of crystal field levels in a staggered
magnetic field.30 Here, we report thermodynamic properties and rare-earth spectroscopy of
Cu3Nd(SeO3)2O2X (X = Cl, Br).
4

Synthesis and characterization
Francisite-type Nd compounds were obtained in sealed under vacuum quartz tubes from mixtures
weighted according to equation: 5CuO + CuX2 + Nd2O3 + 4SeO2 = 2Cu3Nd(SeO3)2O2X (X = Cl,
Br). All used commercially available reagents were at least 99% reagent grade. Selenium dioxide
was obtained by dehydration of H2SeO3 (pure) under vacuum by heating in pump connected glass
tube placed in boiling water. The decomposition product was sublimated in flow of dry air with
NO2 from lead nitrate decomposition. Reaction mixtures were heated in electronically controlled
furnace at 300°C for 12–24 hrs and finally at 575°C for 72 hrs. At the end of the program the
tubes were cooled with the furnace after switching off. Green powder samples were obtained.
The powder XRD (Stoe Stadi-p, CuK1) shows that francisite-type compounds were formed.
The cell constants for Cu3Nd(SeO3)2O2Cl (a = 6.379(3) Å, b = 9.622(4) Å, c = 7.094(3) Å, space
group Pmmn) have been found in a good agreement with data reported previously.13 Structure
refinement for Cu3Nd(SeO3)2O2Br was performed by Rietveld method on STOE Theta/Theta
diffractometer using JANA 2006 software.31 The final refinement parameters and experimental
data are summarized in Table 1. The Rietveld plot for Cu3Nd(SeO3)2O2Br is shown in Fig. 1. The
atomic coordinates and atomic displacement parameters are listed in Table 2. Interatomic
distances are shown in Table 3. The crystal structure of Cu3Nd(SeO3)2O2X (X = Cl, Br) is
organized by buckled layers of corner-sharing CuO6 octahedra. This network is strengthened
additionally by SeO3 triangles. The layers are coupled by Nd ions in octagonal environment
while the chalcogen ions fill the channels in the structure.
Thermodynamic properties
Both ac and dc magnetic susceptibility  and specific heat Cp were measured using relevant
options of commercial “Quantum Design” MPMS-7T and PPMS-9T devices. The temperature
5

dependences of both real  and imaginary  parts of ac magnetic susceptibility in
Cu3Nd(SeO3)2O2X (X = Cl, Br) taken at magnitude of exciting field 5 Oe and frequency 1000 Hz
are shown in Fig. 2. The properties of these compounds differ in both paramagnetic and
magnetically ordered states. In Cl system, real component  apparently follows the Curie-Weiss
law and exhibit sharp anomaly at Neel temperature TN = 34 K. Less pronounced anomaly at this
temperature is seen in . The spin reorientation transition is marked by upturn in  and sharp
peak in  at TR = 4 K. In Br system,  evidences low-dimensional behavior with correlation
maximum most pronounced in  at about 80 K. Two sharp anomalies in  mark Neel transition
at TN = 35.2 K and spin reorientation at TR = 4.6 K. Imaginary component  is insensitive to TN,
but exhibits sharp peak at TR.
The temperature dependences of dc magnetic susceptibility  = M/B in Cu3Nd(SeO3)2O2X (X =
Cl, Br) taken at various fields in zero-filled-cooled regime are shown in Fig. 3. Essentially, the
static and dynamic data agree with each other though no sharp anomalies at either TR or TN can be
detected under high magnetic field. The standard fitting of  vs. T dependence by the Curie–
Weiss law
 = 0 + C/(T - ).
(1)
is not possible for Cu3Nd(SeO3)2O2Br due to pronounced correlation effects far above the Neel
temperature. It can be done for Cu3Nd(SeO3)2O2Cl however. From the data taken at B = 0.1 T in
the range 150–300 K follow 0 = (1.06  0.07)10-3 emu/mol, C = 2.79  0.03 emuK/mol and 
= 18.9  0.8 K. The large positive value of temperature independent term 0 should be attributed
to van Vleck magnetism of Nd3+ ions which significantly exceeds the absolute value of the sum
of diamagnetic Pascal constants32 of individual ions dia =  1.8810-4 emu/mol. The Curie
6

constant C nicely corresponds to the sum of effective magnetic moments of 3Cu2+ ions (S = 1/2)
and Nd3+ ions (J = 9/2, g = 8/11). The Weiss temperature  is positive indicating the
predominance of ferromagnetic exchange interactions at elevated temperatures. Low value of 
as compared to TN signifies fierce competition of ferromagnetic and antiferromagnetic exchange
interactions inherent for francisite-type compounds.
The field dependences of magnetization M in Cu3Nd(SeO3)2O2X (X = Cl, Br) taken at various
temperatures T < TN are shown in Fig. 4. Both compounds evidence the metamagnetic behavior
distinctly different from “standard” spin-flop transition. Surprisingly, the value of magnetization
reached in Br compound at highest field, B = 9 T, is almost triple of that in Cl compound.
Besides, M vs. B curves taken at lowest temperature in these compounds are distinctly different
at low magnetic field.
The difference in magnetic response of Cu3Nd(SeO3)2O2Cl and Cu3Nd(SeO3)2O2Br is evident in
low temperature hysteretic loops, as shown in the insets to Fig. 4. The coercivity at T < TR is
quite appreciable in Cl compound and it is vanishingly small in Br compound. The loop itself is
quite peculiar combining features of both ferromagnetic and antiferromagnetic response. At TR <
T < TN, both systems show no hysteresis but evidence sharp metamagnetic transition at Bm  2 T.
The value of Bm depends on temperature non-monotonously defining a boundary between
antiferromagnetic and canted ferrimagnetic phases.
The findings in magnetization are further supported by the measurements of specific heat Cp. The
temperature dependences of this property in Cu3Nd(SeO3)2O2X (X = Cl, Br) are shown in Fig. 5.
The phase transitions at TR and TN are marked by sharp anomalies clearly seen in Cp/T vs T
representation, as shown in the Insets to Fig. 5. The comparable magnitudes of the anomalies at
7

spin order TN and spin reorientation TR transitions allows suggesting that both of them should be
ascribed to the same magnetic subsystem, i.e. Cu2+ ions.
Optical spectroscopy
The infrared spectroscopy of f-f transitions in Nd3+ ions has been performed to investigate further
the magnetic phase transitions in Cu3Nd(SeO3)2O2X (X = Cl, Br). We use the intrinsic property of
the Kramers doublets to split in a magnetic field, no matter external or internal effective field Beff,
acting on the rare-earth ion by the ordered subsystem of d-metal. Transmittance spectra in a wide
spectral range 1800–15000 cm–1 have been taken using a Fourier–spectrometer Bruker
IFS125HR. Mixtures of Cu3Nd(SeO3)2O2X (X = Cl or Br) and KBr powders were pressed into
tablets with an effective thickness of francisite of about 10 m. Low temperatures have been
reached using an optical closed-cycle cryostat Cryomech PT403.
Several multiplets of Nd3+ ion (4I11/2, 4I13/2, 4I15/2, 4F3/2, 4F5/2+2H9/2, 4F7/2+4S3/2) have been registered in
the spectroscopic range studied. The scheme of Fig. 6a is to explain labeling of the transitions
and the effect of magnetic field on Kramers doublets (KDs). In the crystal field (CF) the
multiplets of the free ion split into the CF levels (marked as I, II, etc. for the ground 4I9/2 multiplet
and as A, B, etc. for the 4I11/2 one). Optical transitions are marked by two labels corresponding to
the initial and the final states of transitions, e.g., IA. In a magnetically ordered state KDs split
depending on the anisotropy of the magnetic g-factors. In a general case, each spectral line splits
into four lines, e.g., spectral line corresponding to the transition IA splits into the lines 1a, 1a,
1a, and 1a. The transitions designated by dashed lines correspond to the spectral lines that
“freeze out” at low temperatures due to the depopulation of the initial state of transition.
8

Temperature behaviour is typical for all the multiplets in both crystals under study, the Fig. 6b-e
demonstrates those for 4I11/2 one. This multiplet is split by a crystal field into J + ½ = 6 Kramers
doublets. Spectral lines IA – IF correspond to the transitions from the ground KD of the ground
4I9/2 multiplet to the KDs of the 4I11/2. Only KD “I” is populated at low enough temperatures, that’s
why there are six transition at temperatures T  15 K, while in the temperature range T  15 K,
the second (or, the “first excited”) level “II” of the ground multiplet with the energy 29 cm-1 is
populated. Correspondingly, the lines denoted as IIA – IIF grow in intensity. With cooling in a
whole temperature range investigated (300–4 K), shift of the spectral lines and growth of CF
splitting denotes the fact of CF strengthening due to the diminishing of the Nd-O distances in the
nearest environment of Nd3+ ion.
The most drastic changes take place in the spectra at the temperatures T < TN. Spectral lines split
as it is shown for the line IA in Figs. 6d,e. The reason for that is splitting of KDs. The Kramers
degeneracy can be lifted only by the action of the magnetic field. Such a field appears in a crystal
due to the AFM ordering of the copper magnetic subsystem. The low-energy components of the
split lines IA and IB “freeze out” at low temperatures. This is unambiguous evidence for the fact
that ground KD splits at TN. Comparison of the spectra of the X = Cl and X = Br compounds
allows concluding that the CF is very similar in both francisites as well as crystallographic
parameters given above, small difference of which leads to small shift of CF level of the Nd3+ ion
( 3 cm-1 for the IA line, see Fig. 6d,e). The splitting of the line IA resembles each other in both
compounds except (i) the temperature of magnetic ordering TN which is  1 K higher in X = Br
francisite in accordance with the data given above and (ii) the value of the splitting of the ground
KD 0 is a bit greater in X = Cl compound (7.4 vs 6.2 cm-1 at 10 K).
9

Temperature dependence of the full width on a half-height (FWHH) for the IA line is given in
Fig. 7 for both compounds together with the lineshapes at several temperatures for the
Cu3Nd(SeO3)2O2Cl. All lineshapes are given in the same spectral region 1961–1981 cm-1. FHWW
of the IA line in both compounds follows intrinsic dependence of diminishing with lowering the
temperature till T  120 K, while, after that it starts to grow till temperature close to the TN. Then,
visible splitting of the spectral line occurs and one can follow the FWHH of one of the line
components. The most interesting is the growth of FHWW with lowering the temperature from T
 120 K to TN. It is known that in the vicinity of the phase transition the spectroscopic parameters
can demonstrate unusual behavior due to the existence of the fluctuations and instabilities when
the system is close to the phase transition (e.g., phonons are broadened at temperatures close to
the structural phase transition).33 This behavior can be regarded as a precursor of the phase
transition.
In low-dimensional magnetic systems, which are the case of francisites, the spin correlations
exist at temperatures well above the temperature of the magnetic ordering34. These spin
correlations form local fluctuating magnetic field Beff, splitting KDs locally. The so-called “tails”
of line splitting in the case of Kramers ions can be found well above the TN, especially in
magnetically low-dimensional systems, and for Nd3+ ion they were registered in 1D magnets
Nd2BaNiO535 at T > 2TN and Nd2BaCuO536 at T > 5TN. So, the growth of the FWHH at
120 K > T > TN in both francisites studied is caused by the “tail” of splittings of Nd3+ KDs by spin
correlations. As was discussed above spin correlations is an intrinsic property of magnetic low-
dimensional system34, while, in francisites being 2D magnets, spin correlations can be caused by
some specific magnetic state, namely, in Cu3Bi(SeO3)2O2Br compound magnetic anisotropy could
be strong enough to impose a quasi-2D XY behavior15 and can exhibit a unique feature - a
10

Kosterlitz–Thouless transition. At temperatures lower than 10 K, the FWHH of the IA line
exhibits minor raise again which can be considered as a precursor of another, low-temperature,
phase transition. This agrees with thermodynamic properties.
Summary
Magnetic phase diagrams of Cu3Nd(SeO3)2O2X (X = Cl, Br) extracted from thermodynamic
measurements are shown in Fig. 8. Four different phases can be distinguished in these diagrams.
PM denotes paramagnetic phase at T > TN, AFM is the antiferromagnetic phase at TR < T < TN at
B < Bm, CFM is the canted ferrimagnetic phase at TR < T < TN at B > Bm, AFMR is the reoriented
antiferromagnetic phase at T < TR.
Rich magnetic phase diagram of Cu3Nd(SeO3)2O2X (X = Cl, Br) stems from the presence and
interaction of the rare-earth and transition metal subsystems. The temperature-induced spin-
reorientation phase transition takes place in the absence of external magnetic field. This
instability in the vicinity of liquid helium temperature may lead to enhanced broadband
absorption of microwave radiation similar to that observed in pristine francisite at metamagnetic
phase transition.
ACKNOWLEDGMENTS
Dr A.V. Olenev is gratefully acknowledged for help with Cu3Nd(SeO3)2O2Br structure
refinement. This work has been supported by the Ministry of Education and Science of the
Russian Federation in the framework of Increase Competitiveness Program of NUST “MISiS”
Grant No. K2-2017-084; by Act 211 of the Government of Russian Federation, Contracts No.
02.A03.21.0004 and No. 02.A03.21.0011. This work has been performed in partial fulfillment of
11

Russian Science Foundation grant RSF 02010 and RFBR grants 18-52-52005, 18-02-00326, 17-
02-00135.
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18

Figure 1. The Rietveld plot for Cu3Nd(SeO3)2O2Br.
Figure 2. Temperature dependences of both real  and imaginary  parts of ac magnetic
susceptibility in Cu3Nd(SeO3)2O2Cl (left panel) and Cu3Nd(SeO3)2O2Br (right panel).
19

Figure 3. Temperature dependences of dc magnetic susceptibility at various magnetic fields in
Cu3Nd(SeO3)2O2Cl (left panel) and Cu3Nd(SeO3)2O2Br (right panel).
Figure 4. Magnetic field dependences of magnetization M at various temperatures in
Cu3Nd(SeO3)2O2Cl (left panel) and Cu3Nd(SeO3)2O2Br (right panel). Insets: Hysteretic loops in
magnetization of Cu3Nd(SeO3)2O2Cl (left panel) and Cu3Nd(SeO3)2O2Br (right panel) at low
temperatures.
20

Figure 5. Temperature dependences of specific heat in Cu3Nd(SeO3)2O2Cl (left panel) and
Cu3Nd(SeO3)2O2Br (right panel). The insets represent Cp/T vs. T curves.
21

Figure 6. (a) Energy level scheme. (b,c) Multiplet 4I11/2 of the Nd3+ ion in Cu3Nd(SeO3)2O2Cl as
(b) transmission spectra at various temperatures, and (c) color map. (d,e) Color maps in the
region of the lowest-frequency spectral line IA of the multiplet for (d) X = Cl (e) X = Br.
Figure 7. The temperature dependence of the full width on the half-height (FWHH) of the IA
4
line of the Nd3+ I11/2 multiplet in both compounds. Insets show the evolution of the lineshapes
with temperature in the same spectral region (shown for T = 24 K) of the IA line for the Cl
compound.
22

Figure 8. Magnetic phase diagrams of Cu3Nd(SeO3)2O2Cl (left panel) and Cu3Nd(SeO3)2O2Br
(right panel). PM – paramagnetic phase, AFM – antiferromagnetic phase, AFMR – reoriented
antiferromagnetic phase, CFM – canted ferrimagnetic phase.
Table 1. Rietveld refinement data for Cu3Nd(SeO3)2O2Br.
Symmetry
Space group
a, Å
Orthorhombic
Pmmn
6.36840(8)
9.64497(14)
7.10058(10)
436.139(10)
2
b, Å
c, Å
V, Å3
Z
Density calc., g/cm3
Instrument
Temperature, K
Wavelength, Å
Software
5.3339
STOE theta/theta
293
1.5418
JANA2006
Absorption coefficient, μ/mm 68.071
2θ range, °
11-110
0.0295
0.0287
1.55
R
wR
Goodness of fit
23

Table 2. Atomic coordinates and isotropic displacement parameters (in Å2) for
Cu3Nd(SeO3)2O2Br.
Atom Position
x
y
z
0.2664
(2)
U
U11
0.0253 0.0248 0.0264
(12) (12) (13)
0.0406 0.041 0.043 -0.0079 0.0006 0.0014
U22
U33
U12
U13
U23
Nd1
Cu1
Cu2
Se1
Br1
O1
2a
4c
2a
4e
2b
4e
8g
4e
1/4
1/4
0
0
0
0
0
0
(19)
0.028
(3)
(2)
0.043
(3)
(3)
0.021
(3)
(16)
0
(19)
0
(18)
0
1/4
1/4
1/4
1/4
1/4
0.7968
(5)
0.5549 0.5971
0.0307 0.0301 0.0244
0
0
0
0
0.0043
(12)
0
(2)
(3)
0.1531
(4)
(17)
0.041
(3)
(17)
0.052
(3)
(15)
0.047
(3)
3/4
0.1092 0.9999 0.038(4)
(12) (14)
0.0445 0.5803 0.7421 0.032(3)
O2
(11)
1/4
(7)
0.1191 0.5825 0.025(4)
(11) (15)
(11)
O3
24

Table 3. Selected interatomic distances (Å) in Cu3Nd(SeO3)2O2Br.
Bond
Distance
Nd1—O1 x2 2.329(11)
Nd1—O2i x4 2.490(7)
Nd1—O3 x2 2.575(11)
Cu1—O2 x2 2.008(8)
Cu1—O1 x2 1.909(6)
Cu2—O1 x2 1.981(11)
Cu2—O3 x2 1.977(11)
Se1—O3
Se1—O2
1.681(11)
x2 1.683(7)
25

26

Basic thermodynamic properties of Nd-francisites are reported
Rare-earth spectroscopy revealed the spin-reorientation
Magnetic phase diagrams of Cu3Nd(SeO3)2O2X (X = Cl, Br) are established
27