Journal of Modern Physics, 2011, 2, 154-157
doi:10.4236/jmp.2011.23023 Published Online March 2011 (
Copyright © 2011 SciRes. JMP
Magnetic, Structural and Morphological Characterization
of Sr2GdRuO6 Double Perovskite
L. T. Corredor1, D. A. Landínez Téllez1, J. L. Pimentel Jr2, P. Pureur2, J. Roa-Rojas1
1Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá
2Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil
Received October 6, 2010; revised December 8, 2010; accepted December 15, 2010
We report structural, morphological and magnetic properties of the Sr2GdRuO6 compound, which is used as
precursor oxide in the production process of RuSr2GdCu2O8 superconducting ruthenocuprates. The crystal-
line structure was studied by X-ray diffraction and Rietveld refinement. Results reveal that material crystal-
lizes in a monoclinic double perovskite, space group P21/n (#14). Scanning Electron Microscopy experi-
ments on samples show homogeneous granular morphology with grain size from 3 up to 7 μm. Semiquanti-
tative analysis of composition was performed by the Energy Dispersive X-ray technique. Experimental re-
sults are 98% in agreement with the theoretical stoichiometry. Curves of magnetization as a function of tem-
perature exhibit an antiferromagnetic-like behaviour, with Néel temperature TN=15.3 K and magnetic effec-
tive moment 8.72 μB.
Keywords: Complex Perovskite, Structure, Magnetic Properties
1. Introduction
The RuSr2GdCu2O8 ruthenocuprate oxide was synthe-
sized for the first time in 1995 [1]. It belongs to the
RuSr2RECu2O8 (Ru-1212RE) family, where RE repre-
sents rare earth elements. The main characteristic of
these compounds is the presence of magnetic and super-
conductor properties in a simultaneous way, with mag-
netic transition temperature higher than the supercon-
ductor critical temperature, which make them unique
respect to the other magnetic superconductors. Initially,
ruthenocuprates were obtained by the solid state reaction
with CuO and Sr2RERuO6 as precursor oxides [2-4]. The
superconductor properties are determined by the Cu-O
bonds in the CuO2 conduction planes, which give rise to
critical temperature values between 15 and 50 K [5].
Magnetic properties are associated with Ru-O bonds
(RuO2), even when actually there is no consensus about
the magnetic ordering between Ru atoms [6]. Muon Spin
Rotation measurements (μSR) point a ferromagnetic or-
dering normal to c crystallographic axis [7], while neu-
tron diffraction experiments indicate an antiferromag-
netic response [8]. The main obstacle to define the nature
of the superconductor-magnetic mechanisms in this kind
of materials is the lack of high purity samples. In order to
enhance the knowledge about the synthesis method of
RuSr2GdCu2O8, we report the high quality production
process, a carefully structural Rietveld analysis of X-ray
diffraction data, morphologic and compositional studies
of the Sr2GdRuO6 material. Measurements of magnetic
susceptibility as a function of temperature were also
performed to observe the possible effects of this precursor
material on the magnetic characteristics of the
RuSr2GdCu2O8 superconductor.
2. Experimental
The Sr2GdRuO6 ceramic was obtained by the standard
solid state reaction method, from stoichiometric quanti-
ties of SrCO3 (Chemi 99.7%), Gd2O3 (Aldrich 99.9%)
and RuO2 (Aldrich 99.9%). In order to extract possible
humidity, the oxide powders were heated to 200oC for
24h. Then they were weighted, grounded in an agatha
mortar, and pressed to form pellets of 9.8 ± 0.1 mm di-
ameter and 1.0 ± 0.1 mm thickness. These pellets were
calcined at 930oC for 12 h, cooled up to ambient tem-
perature, regrounded and twice heated in a sinterization
process at 1230oC for 16 h. Structural characterization
was performed by the X ray diffraction technique (XRD)
through a Panalytical Xpert Pro diffractometer with
CuK = 1,5406 Å radiation. The morphological charac-
terization was carried out by using a FEI Quanta 200
Scanning Electron Microscope SEM, and the semiquan-
titative analysis of composition was performed by means
Energy Dispersive X-ray (EDX) experiments, with an
EDAX microanalysis accessory for the SEM. Magneti-
zation and susceptibility versus temperature measure-
ments were performed through a Quantum Design 2000
MPMS SQUID. Rietveld refinement of experimental
XRD data was performed by using the GSAS code [9].
Refinement results were compared with characteristic
values predicted by the Structure Prediction Diagnostic
Software (SPuDs), which was created for perovskite-like
materials [10].
3. Results and Discussion
Figure 1 shows the powder x-ray diffraction pattern for
Sr2GdRuO6 material. Rietveld refinement of these ex-
perimental data is shown too. The continuous curve cor-
responds to the pattern calculated for Sr2GdRuO6 and the
symbols represent the experimental diffractogram. In the
same graph, locations of Bragg peaks are shown as ver-
tical lines. Curve in bottom of Figure 1 represents the
difference between experimental pattern and the calcu-
lated one. From Rietveld refinement we determined that
this diffraction pattern is characteristic of a monoclinic
perovskite structure, space group P21/n (#14).
The discrepancy factor of refinement was χ2 = 1.063.
The final cell parameters found were a = 5.8019(0) Å,
B = 5.8296(5) Å, c = 8.2223(7) Å, and Tilt Angle
= 90.258o. The atomic coordinates and relative occu-
Figure 1. XRD pattern for Sr2GdRuO6 complex perovskite.
Symbols correspond to the experimental data and continu-
ous one is the obtained by Rietveld refinement. Bottom
curve represents the difference between experimental and
calculated patterns.
pancy of each site are shown in Table 1.
Results are 99 % in agreement with the SPuDs [10],
which predicts P21/n (#14) space group as very probable.
The SPuDs program also predicts the lattice parameters a
= 5.7537 Å, b = 5.9634 Å, c = 8.2760 Å, tolerance factor
0.9170 and tilt angle = 89.9546o. The presence of the
(002), (114) and (116) peaks in the diffractogram of Fig-
ure 1 confirms the existence of the superstructure that
characterizes the A2BB’O6 complex perovskites [11].
The values for the bond distances of cations (relative
to the oxygen anion) and occupancy were obtained from
the Rietveld refinement. These are shown in Table 2.
In this double perovskite the explanation of distortion
from the ideal cubic perovskite structure is clear because
the Sr2GdRu O 6 complex perovskite have the generic
formula A2BBO6, and for this type of material the toler-
ance factor t, is calculated by the ratio:
rr r
where rA, rM’, rM’’ and ro are the ionic radii of the A, B,
B’, and O ions, respectively. If t is equal to unity, there is
ideal cubic perovskite structure, and if t < 1 the struc-
tures is distorted from the cubic symmetry, and in
agreement to the SPuDs prediction [10], the value of
tolerance factor by Sr2GdRuO6 complex perovskite is
0.9170. The distortion from the ideal cubic perovskite
structure is a consequence of the inclination of the
Gd-O6/2 and Ru-O6/2 octahedra; in the mean time support
their corner connectivity. Then, the Ru5+ and Gd3+
cations occupy two crystallographic independent octahe-
dral sites, namely 2d and 2c [12]. Our crystallographic
results are in accordance with other reports, but there is
no an enhanced characterization about atomic positions
and the inter-atomic distances [13].
The alternating distribution between Ru+5 and Gd+3,
ions on the six coordinate B sites of the double
perovskite is in agreement with the results obtained from
the refinement of experimental diffraction pattern. On
the other hand, the Sr2+ is located in the A crystal-
lographicsite, as shown the Figure 2.
The surface morphology of Sr2GdRuO6 samples was
Table 1. Structural parameters of Sr2GdRuO6 found by
Rietveld analysis of XRD data.
Atom Site x y z
Sr 4e 0.5054 0.5309 0.2511
Ru 2c 0.0000 0.5000 0.0000
Gd 2d 0.5000 0.0000 0.5000
O 4e 0.2333 0.2084 0.9773
O 4e 0.2675 0.7408 0.9357
O 4e 0.3856 0.9806 0.2281
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Table 2. Inter-atomic distance and occupancy calculated
through Rietveld refinement of experimental data.
Cation Anion & Multipl. Distance (Å) Occupancy
Ru(2c) O(4e) × 2 1.9681 1.00
Ru(2c) O(4e) × 2 1.9666 1.00
Ru(2c) O(4e) × 2 1.9677 1.00
Gd(2d) O(4e) × 2 2.2823 1.00
Gd(2d) O(4e) × 2 2.2805 1.00
Gd(2d) O(4e) × 2 2.2821 1.00
Sr(4e) O(4e) × 1 3.6412 1.00
Sr(4e) O(4e) × 1 2.8741 1.00
Sr(4e) O(4e) × 1 2.7532 1.00
Sr(4e) O(4e) × 1 2.5319 1.00
Sr(4e) O(4e) × 1 2.9295 1.00
Sr(4e) O(4e) × 1 3.6321 1.00
Sr(4e) O(4e) × 1 2.5176 1.00
Sr(4e) O(4e) × 1 3.7147 1.00
Sr(4e) O(4e) × 1 3.3141 1.00
Sr(4e) O(4e) × 1 2.4884 1.00
Sr(4e) O(4e) × 1 3.4116 1.00
Sr(4e) O(4e) × 1 2.6425 1.00
studied by SEM images as shown in Figure 3. Per-
formed analysis reveals the occurrence of granular to-
pology with size grain between 2 up to 7 µm. As ob-
served in microphotography, grains are strongly diffused
between them. It is important to notice that sample evi-
dences a single type of grain.
Through semiquantitative EDX analysis, we obtain
that composition of material are 98 % in agreement with
theoretical values calculated from stoichiometry of
Sr2GdRuO6 material. Results are shown in Table 3.
It is known that the light characteristic of oxygen on
the application of X-ray radiation produces a subestima-
tion of its concentration in material when EDX technique
is applied to study composition. From structural, mor-
phologic and compositional characterizations we de-
duced that no other crystallographic phases or impurities
are present in the sample.
The magnetic character of material was analyzed from
dc-susceptibility experiments as a function of tempera-
ture. The results are shown in the Figure 4, where the
magnetic susceptibility reveal an anomaly close to T =
15.3 K. This behavior is usually related with the occur-
rence of a magnetic ordering transition. Fitting of sus-
ceptibility with the Curie-Weiss relation 0
CTT reveals that Sr2GdRuO6 behaves as an anti-
ferromagnetic material below a Néel temperature TN =
15.3 K.
In addition, the Curie-Weiss adjust permitted to de-
termine the temperature independent susceptibility
o =
0.0181 emu/mol and the effective magnetic moment
PeffµB = 8.72 µB. Theoretical calculations by the Hund’s
Figure 2. Crystal structure of Sr2GdRuO6. The continuous
black lines indicate the primitive perovskite unit c ell.
Figure 3. SEM micrograph for Sr2GdRuO6 double
perovskite obtained from ETD detector (secondary elec-
Figure 4. Measurements of dc Susceptibility for Sr2GdRuO6
on the application of H = 0.1 T. In picture, circles are the
experimental data and the line represents the Curie-Weiss
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6. References
Table 3. Results of semi quantitative EDX analysis for the
Sr2GdRuO6 sample.
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4. Conclusions
We have performed an experimental study on crystalline
structure, surface morphology, composition and mag-
netic response of Sr2GdRuO6 oxide ceramic. Rietveld
refinement of X-ray diffraction pattern showed that ma-
terial crystallizes in a monoclinic complex perovskite
structure with space group P21/n (#14), with an alternat-
ing distribution between Ru+5 and Gd+3 ions on the six
coordinate B sites of the complex perovskite. The pres-
ence of the crystallographic peaks (002), (114) and (116)
in the diffractogram confirms the existence of the super-
structure that characterizes the A2BBO6, Complex
perovskites. The image of scanning electron microscopy
reveals the strongly compact characteristic of grains with
sizes from 2 up to 7 µm. The results of Energy Disper-
sive X-ray experiments show that the composition of the
material corresponds in a 98% to the expected
stoichiometry of Sr2GdRuO6 complex perovskite. Mag-
netic susceptibility experiments permitted to determine
the occurrence of a paramagnetic-antiferromagnetic tran-
sition with a Néel temperature of 15.3 K. From the
analysis of susceptibility curves we found the effective
magnetic moment to be 8.72µB. In the dc susceptibility
curve it is possible to observe a tendency to the anti-
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5. Acknowledgements
This work was partially supported by the Colombian
agencies Colciencias, the Division of Investigations,
Universidad Nacional de Colombia (DIB - Bogotá), and
Brazilian CNPq.