On the existence of a new phase in SASD
Neutron irradiation induced paramagnetic centers are investigated using EPR. It is shown that the observed EPR signal appears to be mainly due to a variety of radicals. Temperature dependence of the EPR linewidth is attempted to be correlated both with the results supplied by inelastic neutron s...
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Інститут фізики конденсованих систем НАН України
2003
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| Назва видання: | Condensed Matter Physics |
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| Цитувати: | On the existence of a new phase in SASD / I.E. Lipinski, J. Kuriata, N.A. Korynevskii // Condensed Matter Physics. — 2003. — Т. 6, № 2(34). — С. 245-250. — Бібліогр.: 8 назв. — англ. |
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irk-123456789-1207082017-06-13T03:06:40Z On the existence of a new phase in SASD Lipinski, I.E. Kuriata, J. Korynevskii, N.A. Neutron irradiation induced paramagnetic centers are investigated using EPR. It is shown that the observed EPR signal appears to be mainly due to a variety of radicals. Temperature dependence of the EPR linewidth is attempted to be correlated both with the results supplied by inelastic neutron scattering spectra and by the recently developed theoretical model for phase transitions in sodium ammonium sulphate dihydrate type crystals. Парамагнітні центри, індуковані завдяки опроміненню нейтронами кристалу SASD, досліджуються методом ЕПР. Доведено, що спостережуваний ЕПР-сигнал походить від різноманітного типу радикалів SO−n . Встановлено кореляцію між температурнозалежною шириною лінії цього сигналу і спектром непружного розсіяння нейтронів, а також із нещодавно запропонованою теоретичною моделлю фазових переходів y сполуках типу амонієво-натрієвого дигідрату сірки. 2003 Article On the existence of a new phase in SASD / I.E. Lipinski, J. Kuriata, N.A. Korynevskii // Condensed Matter Physics. — 2003. — Т. 6, № 2(34). — С. 245-250. — Бібліогр.: 8 назв. — англ. 1607-324X PACS: 76.30.K, 77.80.Bh DOI:10.5488/CMP.6.2.245 http://dspace.nbuv.gov.ua/handle/123456789/120708 en Condensed Matter Physics Інститут фізики конденсованих систем НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
| description |
Neutron irradiation induced paramagnetic centers are investigated using
EPR. It is shown that the observed EPR signal appears to be mainly due
to a variety of radicals. Temperature dependence of the EPR linewidth is
attempted to be correlated both with the results supplied by inelastic neutron
scattering spectra and by the recently developed theoretical model for
phase transitions in sodium ammonium sulphate dihydrate type crystals. |
| format |
Article |
| author |
Lipinski, I.E. Kuriata, J. Korynevskii, N.A. |
| spellingShingle |
Lipinski, I.E. Kuriata, J. Korynevskii, N.A. On the existence of a new phase in SASD Condensed Matter Physics |
| author_facet |
Lipinski, I.E. Kuriata, J. Korynevskii, N.A. |
| author_sort |
Lipinski, I.E. |
| title |
On the existence of a new phase in SASD |
| title_short |
On the existence of a new phase in SASD |
| title_full |
On the existence of a new phase in SASD |
| title_fullStr |
On the existence of a new phase in SASD |
| title_full_unstemmed |
On the existence of a new phase in SASD |
| title_sort |
on the existence of a new phase in sasd |
| publisher |
Інститут фізики конденсованих систем НАН України |
| publishDate |
2003 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/120708 |
| citation_txt |
On the existence of a new phase
in SASD / I.E. Lipinski, J. Kuriata, N.A. Korynevskii // Condensed Matter Physics. — 2003. — Т. 6, № 2(34). — С. 245-250. — Бібліогр.: 8 назв. — англ. |
| series |
Condensed Matter Physics |
| work_keys_str_mv |
AT lipinskiie ontheexistenceofanewphaseinsasd AT kuriataj ontheexistenceofanewphaseinsasd AT korynevskiina ontheexistenceofanewphaseinsasd |
| first_indexed |
2025-07-08T18:26:39Z |
| last_indexed |
2025-07-08T18:26:39Z |
| _version_ |
1837104314501300224 |
| fulltext |
Condensed Matter Physics, 2003, Vol. 6, No. 2(34), pp. 245–250
On the existence of a new phase
in SASD
I.E.Lipinski 1 , J.Kuriata 1 , N.A.Korynevskii 2,3
1 Institute of Physics, Technical University of Szczecin,
17 Aleja Piastow, 71–310 Szczecin, Poland
2 Institute for Condensed Matter Physics
of the National Academy of Sciences of Ukraine,
1 Svientsitskii Str., 79011 Lviv, Ukraine
3 Institute of Physics, University of Szczecin,
15 Wielkopolska Str., 70–451 Szczecin, Poland
Received September 13, 2002
Neutron irradiation induced paramagnetic centers are investigated using
EPR. It is shown that the observed EPR signal appears to be mainly due
to a variety of radicals. Temperature dependence of the EPR linewidth is
attempted to be correlated both with the results supplied by inelastic neu-
tron scattering spectra and by the recently developed theoretical model for
phase transitions in sodium ammonium sulphate dihydrate type crystals.
Key words: sodium ammonium sulphate dihydrate, electron
paramagnetic resonance, phase transitions
PACS: 76.30.K, 77.80.Bh
1. Introduction
Sodium ammonium sulphate dihydrate (SASD) and sodium ammonium selenate
dihydrate (SASeD) are orthorhombic with space group P21 and four molecules in
the unit cell in the paraelectric phase [1] and P212121 in the ferroelectric phase
[2]. The crystal structure of SASD may be considered to consist of NaO6 octahe-
dra, sharing three O atoms on a face, aligned along [100], interlaced with chains of
(NH+
4 ) − (SO2−
4
) − (NH+
4
) with the two types of chain being linked by sharing one
O in the SO4 tetrahedra and hydrogen bonds.
The crystal undergoes the first-order transition from para- to ferroelectric phase
at 101 K.
Many experimental methods have been used in order to derive some informa-
tion about the nature of phase transitions taking place in SASD type crystals. The
spectroscopic methods used so far seem to be most effective. In this context, it is
c© I.E.Lipinski, J.Kuriata, N.A.Korynevskii 245
I.E.Lipinski, J.Kuriata, N.A.Korynevskii
worthwhile mentioning two electron paramagnetic resonance (EPR) studies of radi-
ation induced paramagnetic centers. The first one is reported in [3] and deals with
γ-irradiated SASeD powder and single crystals. The induced centers were identified
as being due to SeO−2 and SeO−3 and SeO−4 radicals. The phase transition presented
itself by a small change in the structure and the components of both the g- and
the A-tensors. The second one, is reported in [4] and describes the behaviour of
X-irradiation induced centers in SASD. The observed EPR spectrum was very com-
plex because it proved to be due to the contribution of at least eight different type
centers. Probably the complexity of the EPR spectrum hindered the possibility of a
closer inspection of the effect of the phase transition on the spectrum.
This paper describes our new results obtained for neutron-irradiation induced
centers in SASD.
2. Experimental
The powdered samples of SASD used for EPR measurements were taken from
the bulk sample used previously in neutron scattering studies carried out using
the NERA inverted geometry time-of-flight spectrometer with the neutron source
being the IBR-2 high-flux pulsed reactor working at the JINR in Dubna. The bulk
sample was subjected to neutron irradiation for four days. The EPR studies were
accomplished one month later because straight after the irradiation the sample was
highly radioactive. EPR measurements were carried out using a standard X-band
spectrometer operating with 100 kHz modulation of the steady magnetic field. The
spectra were observed in the temperature range from 300 K to 30 K.
3. Results and discussion
As mentioned above, prior to EPR measurements, neutron diffraction and inelas-
tic neutron scattering spectra had been measured. The results of this experiment are
described in [5]. The temperature neutron diffraction spectrum could be fitted with
the known X-ray diffraction studies [1], supporting the X-ray diffraction dilatometry
measurements of Osaka [6], and exhibited a sudden change below Tc = 101 K. Thus,
these spectra clearly showed that the material we used in the neutron experiment
was correctly chosen.
Much more interesting results were obtained for the inelastic neutron scattering
spectra shown in figure 1 in the form of the generalized phonon density of states
G(ω).
A particular behaviour of the system under discussion was found for ω < 50 cm−1
(i.e. the region at which the crystal dynamics plays the dominant role). Below 110 K
and above 160 K the generalized phonon density of states is proportional to ω2. This
means, as is well known, that here we deal with the dynamics represented by the
ordered crystal. However, in the temperature range from about 160 K to 110 K the
G(ω) is linear in ω.
246
On the existence of a new phase in SASD
Figure 1. Temperature dependence of the generalized phonon density of states.
280 300 320 340 360
g
xx'
g
yy
(SO
3
_ )
g
yy
(SO
2
_ )
B [mT]
Figure 2. EPR spectrum of neutron in-
duced paramagnetic centers in SASD.
Two physically different interpreta-
tions may be given to account for such
a behaviour: either in this temperature
range the system has a character of the
orientational proton glass, or one de-
tects a precursor signal of the incipi-
ent instability connected with a soft op-
tic mode responsible for the ferroelectric
phase transition.
In order to obtain some additional
information, EPR measurements were
carried out on the samples taken from
the bulk material used for neutron stud-
ies. They proved that the observed EPR
spectrum (see figure 2) is relatively sim-
ple (compared to those obtained by X-
ray irradiation) and is very similar to
those described in [3]. Following the
identification procedure given in [3] we
ascribe this spectrum to SO−
n
type rad-
icals (with n = 2, 3, 4).
It is worth noting here that the re-
sults of the measurements reported in
[3] were taken only in two temperature
points: at 300 K (i.e. above Tc) and at
77 K (i.e. below Tc).
247
I.E.Lipinski, J.Kuriata, N.A.Korynevskii
Figure 3. The temperature dependence of the EPR linewidth for SASD measured
for neutron irradiation induced paramagnetic centers.
However, the data obtained there indicated for the distortion of the SO−
4 radical.
This radical undergoes rapid reorientations at room temperature. As the tempera-
ture is reduced the g-tensor begins to show rhombic symmetry because of the slowing
down of the SO−4 reorientations near Tc leading to the appearance of a new structure
involving hydrogen bonds.
We have measured the temperature dependence of the neutron induced param-
agnetic centers in the temperature range from 300 to 90 K. Like in [3], we found that
below Tc one observes a small change in the components of the g-tensor for both
radicals. However, the temperature dependence of the EPR linewidth of the narrow
line (see figure 2) shows a particular behaviour in the temperature range from 190
to 140 K. In this temperature range the EPR linewidth changes essentially, what
approximately reproduces the behaviour of the generalized phonon density of states.
Furthermore, we have seen quite significant hysteresis shown in figure 3. On the
basis of this observation we incline to accept that indeed a new phase appears in
the system before it undergoes a phase transition.
Based on experimental data obtained mainly from EPR studies, a new theoreti-
cal model for the nature of the phase transitions taking place in SASD type crystals
has been suggested [7–8]. The model takes into account that SO4(SeO4) groups
contribute predominantly to the phase transitions occurring in these crystals. The
modified Mitsui-type model, which includes both long- and short-range correlations
has been used. The Mitsui Hamiltonian, formulated in the cluster form and applied
to two-sublattice case showed that for the system under discussion one can distin-
guish two order parameters: the usual polarization P and a new one ξ. This latter
parameter reflects an antiferroelectric type coupling taking place in each particular
248
On the existence of a new phase in SASD
Figure 4. Temperature dependence of eight ξ-branches. The curves indicated
by dotted points correspond to real solutions for ξ ensuring the minimum of
free energy. The arrows show temperature points at which the system undergoes
transitions from one branch to another.
cell. The temperature dependence of these parameters was obtained minimizing the
free energy with respect to the P and ξ parameters. In the context of this paper,
the temperature dependence of ξ parameter is of particular interest. This depen-
dence is shown in figure 4. Generally, in the whole temperature range there are eight
branches of ξ. It is interesting to note that the particular behaviour of ξ is observed
in the temperature range Tc < T < T2. This temperature range correlates quite well
with the EPR data on the temperature dependence of the linewidth. We do not yet
exactly know how both the experimental and the theoretical facts described above
can be reasonably linked. However, the anomalies detected by neutron and EPR
studies as well as theoretical considerations seem to indicate that some new phase
of the material under discussion exists in the region from Tc to T = 200 K.
References
1. Corrazzo E., Sabelli C., Guiseppetti G. // Acta Crystallogr., 1967, vol. 22, p. 683.
2. Aleksandrov K.S., Aleksandrova I.P., Shabanov V.F., Yuzvak V.I., Nozik Y.Z.,
Fikin L.I. // Phys. Status Solidi (a), 1978, vol. 45, p. 53.
3. Ramani K., Srinivasan R. // Mol. Phys., 1981, vol. 44, p. 125.
4. Baker J.M., Cook M.I., Tronconi A.L., Kuriata J., Sadlowski L. // J. Phys.: Condens.
Matter, 1993, vol. 5, p. 459.
249
I.E.Lipinski, J.Kuriata, N.A.Korynevskii
5. Lipinski I.E., Kuriata J., Natkaniec I., Pawlukojc A. // Phys. Status Solidi (b), 2001,
vol. 227, p. 477.
6. Osaka T. // J. Phys. Soc. Japan, 1978, vol. 45, p. 571.
7. Kuriata J., Lipinski I.E., Korynevskii N.A., Bodziony T. // Physica B, 2001, vol. 307,
p. 203.
8. Lipinski I.E., Korynevskii N.A., Kuriata J., Pastusiak W. // Physica B, 2003, vol. 327,
p. 116.
Про існування нової фази в SASD
І.Е.Ліпіньскі 1 , Є.Куріата 1 , М.А.Кориневський 2,3
1 Інститут фізики, Політехніка Щецінська,
Польща, 71–310 Щецін, Алея Піастув, 17
2 Інститут фізики конденсованих систем НАН України,
79011 Львів, вул. Свєнціцького, 1
3 Інститут фізики, Щецінський університет,
Польща, 70–451 Щецін, вул. Вєлькопольська, 15
Отримано 13 вересня 2002 р.
Парамагнітні центри, індуковані завдяки опроміненню нейтронами
кристалу SASD, досліджуються методом ЕПР. Доведено, що спосте-
режуваний ЕПР-сигнал походить від різноманітного типу радикалів
SO−
n
. Встановлено кореляцію між температурнозалежною шириною
лінії цього сигналу і спектром непружного розсіяння нейтронів, а та-
кож із нещодавно запропонованою теоретичною моделлю фазових
переходів y сполуках типу амонієво-натрієвого дигідрату сірки.
Ключові слова: амонієво-натрієвий дигідрат сірки, електронний
парамагнітний резонанс, фазові переходи
PACS: 76.30.K, 77.80.Bh
250
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