Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites
The analysis of the ESR spectra for the powdered samples of (Ca,Na)-doped manganites have been performed in the temperature range 220–320 K. It is shown that the samples under investigation are characterized by a broadened para- to ferromagnetic transition and complicated spectra within the transiti...
Збережено в:
| Дата: | 2009 |
|---|---|
| Автори: | , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
2009
|
| Назва видання: | Физика низких температур |
| Теми: | |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/116983 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites / A.I. Tovstolytkin, A.M. Pogorily, D.I. Podyalovskii // Физика низких температур. — 2009. — Т. 35, № 2. — С. 173-176. — Бібліогр.: 21 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-116983 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-1169832017-05-19T03:03:05Z Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites Tovstolytkin, A.I. Pogorily, A.M. Podyalovskii, D.I. Низкотемпеpатуpный магнетизм The analysis of the ESR spectra for the powdered samples of (Ca,Na)-doped manganites have been performed in the temperature range 220–320 K. It is shown that the samples under investigation are characterized by a broadened para- to ferromagnetic transition and complicated spectra within the transitional region. The conclusion is made that the satisfactory interpretation of the resonance data is only possible if the interference of the coexisting phases is taken into account within the transitional region. Under these conditions, the resonance field for the paramagnetic phase is shown to increase with the temperature lowering, while that for the ferromagnetic phase first decreases and then approaches a value characteristic of the uniformly magnetized ferromagnetic sample. It is noted that the results obtained are in compliance with those predicted theoretically for the spherical particles containing a mixture of the paramagnetic and ferromagnetic phases. 2009 Article Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites / A.I. Tovstolytkin, A.M. Pogorily, D.I. Podyalovskii // Физика низких температур. — 2009. — Т. 35, № 2. — С. 173-176. — Бібліогр.: 21 назв. — англ. PACS: 76.50.+g, 75.30.Kz, 75.47.Gk http://dspace.nbuv.gov.ua/handle/123456789/116983 en Физика низких температур Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Низкотемпеpатуpный магнетизм Низкотемпеpатуpный магнетизм |
| spellingShingle |
Низкотемпеpатуpный магнетизм Низкотемпеpатуpный магнетизм Tovstolytkin, A.I. Pogorily, A.M. Podyalovskii, D.I. Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites Физика низких температур |
| description |
The analysis of the ESR spectra for the powdered samples of (Ca,Na)-doped manganites have been performed in the temperature range 220–320 K. It is shown that the samples under investigation are characterized by a broadened para- to ferromagnetic transition and complicated spectra within the transitional region. The conclusion is made that the satisfactory interpretation of the resonance data is only possible if the interference of the coexisting phases is taken into account within the transitional region. Under these conditions, the resonance field for the paramagnetic phase is shown to increase with the temperature lowering, while that for the ferromagnetic phase first decreases and then approaches a value characteristic of the uniformly magnetized ferromagnetic sample. It is noted that the results obtained are in compliance with those predicted theoretically for the spherical particles containing a mixture of the paramagnetic and ferromagnetic phases. |
| format |
Article |
| author |
Tovstolytkin, A.I. Pogorily, A.M. Podyalovskii, D.I. |
| author_facet |
Tovstolytkin, A.I. Pogorily, A.M. Podyalovskii, D.I. |
| author_sort |
Tovstolytkin, A.I. |
| title |
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites |
| title_short |
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites |
| title_full |
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites |
| title_fullStr |
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites |
| title_full_unstemmed |
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites |
| title_sort |
peculiar features of electron spin resonance spectra in (ca,na)-doped lanthanum manganites |
| publisher |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| publishDate |
2009 |
| topic_facet |
Низкотемпеpатуpный магнетизм |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/116983 |
| citation_txt |
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites / A.I. Tovstolytkin, A.M. Pogorily, D.I. Podyalovskii // Физика низких температур. — 2009. — Т. 35, № 2. — С. 173-176. — Бібліогр.: 21 назв. — англ. |
| series |
Физика низких температур |
| work_keys_str_mv |
AT tovstolytkinai peculiarfeaturesofelectronspinresonancespectraincanadopedlanthanummanganites AT pogorilyam peculiarfeaturesofelectronspinresonancespectraincanadopedlanthanummanganites AT podyalovskiidi peculiarfeaturesofelectronspinresonancespectraincanadopedlanthanummanganites |
| first_indexed |
2025-07-08T11:24:43Z |
| last_indexed |
2025-07-08T11:24:43Z |
| _version_ |
1837077768123187200 |
| fulltext |
Fizika Nizkikh Temperatur, 2009, v. 35, No. 2, p. 173–176
Peculiar features of electron spin resonance spectra
in (Ca,Na)-doped lanthanum manganites
A.I. Tovstolytkin, A.M. Pogorily, and D.I. Podyalovskii
Institute of Magnetism, 36-b Vernadskogo Blvd., Kyiv 03142, Ukraine
E-mail: atov@imag.kiev.ua
Received September 19, 2008
The analysis of the ESR spectra for the powdered samples of (Ca,Na)-doped manganites have been per-
formed in the temperature range 220–320 K. It is shown that the samples under investigation are character-
ized by a broadened para- to ferromagnetic transition and complicated spectra within the transitional region.
The conclusion is made that the satisfactory interpretation of the resonance data is only possible if the inter-
ference of the coexisting phases is taken into account within the transitional region. Under these conditions,
the resonance field for the paramagnetic phase is shown to increase with the temperature lowering, while
that for the ferromagnetic phase first decreases and then approaches a value characteristic of the uniformly
magnetized ferromagnetic sample. It is noted that the results obtained are in compliance with those pre-
dicted theoretically for the spherical particles containing a mixture of the paramagnetic and ferromagnetic
phases.
PACS: 76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance;
75.30.Kz Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.);
75.47.Gk Colossal magnetoresistance.
Keywords: electron spin resonance, magnetic phase coexistence, doped lanthanum manganites.
Electrically conducting ferromagnetic materials where
the conduction electrons have a high mobility and are
fully spin-polarized are desirable for realizing thin-film
spin electronic devices [1,2]. The doped manganite sys-
tems La1–xMxMnO3 (M = alkaline or alkaline earth ele-
ment), due to their half-metallic ferromagnetic nature and
the concomitant complete spin polarization, have been
considered as very promising materials for the creation of
spin emitters and filters in magnetic nanostructures.
Recent theoretical and experimental studies have
shown that the essential physics of doped manganites
stems from a strongly pronounced tendency towards mag-
netic phase separation, which often makes an inhomo-
geneous state more preferable than a homogeneous one
[3–5]. Electron spin resonance (ESR) is an advantageous
tool to probe the manganite behavior within the regions of
phase coexistence but the interpretation of the results is
far from being unambiguous [6–8]. It is the mutual influ-
ence of coexisting phases that may strongly change the
resonance conditions for each of the coexisting phases
[6,9,10].
The analysis of the behavior of the system in which
paramagnetic (PM) and ferromagnetic (FM) phases coex-
ist over a wide temperature range was carried out in
Refs. 6 and 10. Drastic transformations of the resonance
spectra are predicted for the region of the phase coexis-
tence. The fact that the FM phase doesn’t occupy the
whole volume of a particle changes the resonance condi-
tions for the FM phase, as they in the first place are gov-
erned by the shape of FM regions [11]. On the other hand,
the magnetic fields created by the FM regions strongly
transform the resonance conditions for the PM phase
[6,10].
To date, there have been only few works with the rea-
sonable interpretation of experimental data within the
temperature range where the FM and PM phases coexist
[6,9,12,13]. To clarify the picture, one should carry out a
comprehensive analysis of the ESR spectra on the care-
fully characterized samples with a broadened magnetic
transition. As follows from the studies of magnetic prop-
erties, the most suitable samples for this aim are Ca- and
Na(K)-doped lanthanum manganites, the peculiar feature
of which is a wide temperature range of the PM and FM
phases coexistence [14–17]. Here, we present the results
of the ESR measurements in (Ca,Na)-doped lanthanum
manganites, which clearly show that coexisting phases
© A.I. Tovstolytkin, A.M. Pogorily, and D.I. Podyalovskii, 2009
cannot be considered as independent and their mutual in-
fluence should be taken into account.
To extend the width of the magnetic transition, we
synthesized the samples with the excessive amount of
structural vacancies in a lanthanum sublattice. To do this,
the bulk polycrystalline samples with the nominal che-
mical formula La0.7+xCa0.3–2xNaxMnO3 were prepared,
where the substitution was made according to the scheme
2Ca → La + Na. The reason for the vacancy formation
was enhanced sodium volatility at high temperatures [15].
The details of the samples' preparation and characteriza-
tion are described in Refs. 15, 16, 18. The ESR investiga-
tions were performed on the powdered samples with x =
= 0.04 and 0.08. The powder consisted of micrometer-
sized particles whose shape was close to the spherical
one. The measurements were carried out with the use of
X-band EPR spectrometer Radiopan SE/X-2544 (opera-
ting frequency ν ≈ 9.2 GHz) in the temperature range
220–320 K.
Figures 1 and 2 show the features of the temperature
evolution of the ESR spectra for the sample with x = 0.04.
In a high-temperature region (T > 304 K), the spectrum
consists of a single symmetric line L1 which keeps dis-
cernible down to 280 K. At T = 320 K, the integrated
curve is well fitted by a Lorentzian with the parameters
which correspond to the paramagnetic state of manganites
(resonance field B L
0
1 ≈ 318 mT, linewidth wL1 ≈ 44 mT)
[9,10,12]. With the temperature lowering, the resonance
field of this line remains almost constant, but the line-
width gradually increases. As T crosses 304 K, the inte-
grated curve deviates from the Lorentzian. The analysis
shows that the experimental curve cannot be decomposed
into two lines any longer: a satisfactory description can
only be achieved when one involve three lines — L1 and
two additional ones (see Fig. 2). These additional lines
have the shape of Gaussians with the resonance fields
higher (L2) and lower (L3) than B L
0
1. With the further de-
crease in temperature, the intensity of L1 diminishes and
the spectra can be satisfactory described as consisting of
the lines L2 and L3 (240 K ≤ T < 280 K) or L3 only
(T < 240 K). At T < 274 K another, low-field line appears
(marked by dashed ellipses in Figs. 1 and 2), the nature of
which was discussed in Refs.19–21. The analysis of its
behavior is beyond the frames of this work.
It should be noted that the spectra consisting of two
Gaussians, one being centered at B > B L
0
1 and another at
B < B L
0
1, were predicted in Ref. 10 for a spherical particle
containing a mixture of the PM and FM phases. In our
case, the coexistence of these lines with L1 may imply
that although the FM phase is nucleated in some of the
powder particles, the rest of them still remains purely
paramagnetic within a certain temperature range.
174 Fizika Nizkikh Temperatur, 2009, v. 35, No. 2
A.I. Tovstolytkin, A.M. Pogorily, and D.I. Podyalovskii
220 K
E
S
R
S
ig
n
al
B, mT
320 K
x = 0.04
0 300 600
Fig. 1. Temperature evolution of the ESR spectra for
La0.7+xCa0.3–2xNaxMnO3 with x = 0.04. A dashed ellipse marks
the low-field line which is not subjected to the analysis in this
work.
220 K
250 K
290 K
E
S
R
si
g
n
al
T = 320 K
x = 0.04
0 300 600
B, mT
Fig. 2. Experimental (open circles) and fitted (solid lines) re-
sonance curves for the sample with x = 0.04.
Analyze the behavior of the ESR spectra in more de-
tails. Figure 3,a shows the temperature dependences of
the resonance fields for the lines L1–L3. As was noted
above, B L
0
1 remains almost constant and doesn’t exhibit
noticeable changes with temperature. On the contrary, the
resonance fields for the other two lines undergo drastic
changes. With the temperature lowering, B L
0
2 displays
a monotonic increase, but B L
0
3 first decreases, reaches
a minimum, then grows and eventually keeps almost
constant after reaching the value which is close to B L
0
1.
It is noteworthy that a similar picture was also re-
ported in Ref. 12 for the powdered bulk samples of
(La,Pr,Pb)Mn1–xCuxO3.
After the integrated spectrum was decomposed into N
lines and the area ALi under ith line was found, the relative
intensity of each of the lines was calculated according to
the formula: A A ALi Li Li
i
N
rel =
=
∑/
1
. Figure 3,b shows the
values of A Li
rel as functions of temperature. It is seen that
for the temperatures beyond the transitional region
(240–304 K), the ESR spectrum consists of a single line,
namely, L1 at high temperatures or L3 at low tempera-
tures. This allows us to associate the line L1 with the PM
phase and L3 with the FM one. Within the transitional re-
gion, the temperature dependences of the relative inten-
sity of these lines display the monotonic and opposite
trends, as is expected for the case of a broadened PM to
FM transition. The behavior of the line L2 which exists
only within the transitional region is somewhat unusual
and its nature needs to be discussed further.
The analysis of the ESR spectra for a spherical particle
in which the PM and FM phases coexist over a wide tem-
perature range was carried out in Ref. 10. It was shown
that the mutual influence of the coexisting phases results
in the following effects: the resonance field for the PM
phase increases with the temperature lowering, while that
for the FM phase first decreases and then approaches a
value characteristic of the uniformly magnetized ferro-
magnetic sample. Applying this scenario to our case, we
should expect that, since the shape of the particles is close
to the sphere, the resonance field for the line L3 should
approach B L
0
1 at low temperatures [11], and this is actually
observed in experiment (see Fig. 3,a). As is also seen
from Fig. 3, the behavior of L2 well agrees with what is
predicted for the paramagnetic resonance signal for the
case where the PM phase coexists with the FM one and
senses the action of its effective field [10]. The line L1, as
was noted above, originates from the particles which are
purely paramagnetic.
When the transition is extremely broadened, the lines
L2 and L3 can coexist down to the lowest temperatures. It
seems that Fig. 4 reflects just this case. For the sample
La0.7+xCa0.3–2xNaxMnO3 with x = 0.08, the intensities of
the lines L2 and L3 are comparable at the lowest tempera-
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites
Fizika Nizkikh Temperatur, 2009, v. 35, No. 2 175
250
500
L1
L3
L2
L1
L3
b
a
L2
x = 0.04
240 320
0
50
100
T, K
B
,
m
T
0
A
,
%
re
l
Fig. 3. Resonance fields (a) and relative intensities (b) of the
lines L1–L3 for La0.7+xCa0.3–2xNaxMnO3 with x = 0.04.
200
300
400
L1
L3
L2
L1
L3
b
a
L2
x = 0.08
240 320
0
50
100
T, K
B
,
m
T
0
A
,
%
re
l
Fig. 4. Resonance fields (a) and relative intensities (b) of the
lines L1–L3 for La0.7+xCa0.3–2xNaxMnO3 with x = 0.08.
tures achievable in our measurement setup (220 K) and,
thus, we were unable to observe the situation where L3
becomes dominant. It is noteworthy that similar results
were reported by other research groups on a number of the
doped manganite compounds [6,9,12,13,19].
In summary, the analysis of the ESR spectra for the
powdered samples of La0.7+xCa0.3–2xNaxMnO3 with x =
= 0.04 and 0.08 have been performed over a wide temper-
ature range. It is shown that for the temperatures beyond
the transitional region, the integrated curve is well de-
scribed by a single line, namely, by the Lorentzian in the
purely PM state and the Gaussian in the purely FM state.
Within the transitional region, the resonance spectra be-
come more complicated and this especially concerns the
particles, in which the PM and FM phases coexist. In the
latter case, the reasonable interpretation of the observed
spectra is only possible when the interference of the coex-
isting phases is taken into account. Under these condi-
tions, the resonance field for the PM phase increases with
the temperature lowering, while that for the FM phase
first decreases and then approaches a value characteristic
of the uniformly magnetized ferromagnetic sample,
which is in compliance with the results predicted in
Ref. 10 for the spherical particles containing a mixture of
the PM and FM phases.
The work is partly supported by the Science and Tech-
nology Centre in Ukraine, project #4912.
1. J.M.D. Coey and S. Sanvito, J. Phys. D: Appl. Phys. 37,
988 (2004).
2. A. Gupta and J.Z. Sun, J. Magn. Magn. Mater. 200, 24
(1999).
3. E. Dagotto, T. Hotta, and A. Moreo, Phys. Rep. 344, 1
(2001).
4. V.M. Loktev and Yu.G. Pogorelov, Fiz. Nizk. Temp. 26,
231 (2000) [Low Temp. Phys. 26, 171 (2000)].
5. S.L. Yuan, Y.P. Yang, Z.C. Xia, L. Liu, G.H. Zhang, W.
Feng, J. Tang, L.J. Zhang, and S. Liu, Phys. Rev. B66,
172402 (2002).
6. N.O. Moreno, P.G. Pagliuso, C. Rettory, G.S. Gardner, J.L.
Sarrao, J.D. Thompson, D.L. Huber, J.F. Mitchell, J.J. Mar-
tinez, and S.B. Oseroff, Phys. Rev. B63, 174413 (2001).
7. A. Tovstolytkin, A. Pogorily, A. Vovk, D. Podyalovskii, I.
Lezhnenko, and A. Matviyenko, J. Magn. Magn. Mater.
272–276, 1839 (2004).
8. A. Shengelaya, Guo-Meng Zhao, H. Keller, and K.A. M�l-
ler, Phys. Rev. Lett. 26, 5296 (1996).
9. K.W. Joh, C.H. Lee, C.E. Lee, N.H. Hur, and H.-C. Ri, J.
Phys.: Condens. Matter 15, 4161 (2003).
10. Yu.I. Dzhezherya and A.I. Tovstolytkin, J. Phys.: Con-
dens. Matter 19, 246212 (2007).
11. A.G. Gurevich and G.A. Melkov, Magnetization Oscilla-
tions and Waves, New York: CRC (1996).
12. T.L. Phan, N.D. Tho, M.H. Phand, N.D. Ha, N. Chau, and
S.C. Yu, Physica B371, 317 (2006).
13. E. Winkler, M.T. Causa, and C.A. Ramos, Physica B398,
434 (2007).
14. K. D�rr, J. Phys. D: Appl. Phys. 39, 125 (2006).
15. O.Z. Yanchevskii, A.I. Tovstolytkin, O.I. V'yunov, D.A.
Durilin, and A.G. Belous, Inorg. Mater. 40, 744 (2004).
16. A.I. Tovstolytkin, A.M. Pogorily, D.I. Podyalovskii, V.M.
Kalita, A.F. Lozenko, P.O. Trotsenko, S.M. Ryabchenko,
A.G. Belous, O.I. V'yunov, and O.Z. Yanchevskii, J. Appl.
Phys. 102, 063902 (2007).
17. S.L. Ye, W.H. Song, J.M. Dai, K.Y. Wang, S.G. Wang, J.J.
Du, Y.P. Sun, J. Fang, J.L. Chen, and B.J. Gao, J. Appl.
Phys. 90, 2943 (2001).
18. A.I. Tovstolytkin, A.M. Pogorily, Yu.I. Dzhezherya, D.I.
Podyalovskii, and V.A. Lysenko, Proc. 20th Int. Conf.
«New Magnetic Materials of Microelectronics», Moscow,
Russia, June 12–14, 2006, 654 (2006).
19. E. Winkler, M.T. Causa, C.A. Ramos, and E. De Biasi,
Physica B354, 51 (2004).
20. D.L. Lyfar, S.M. Ryabchenko, V.N. Krivoruchko, S.I.
Khartsev, and A.M. Grishin, Phys. Rev. B69, 100409 (R)
(2004).
21. D.K. Aswal, A. Singh, R.M. Kadam, M.K. Bhide, A.G.
Page, S. Bhattacharya, S. Gupta, Y.V. Yakhmi, and V.C.
Sahni, Mater. Lett. 59, 728 (2005).
176 Fizika Nizkikh Temperatur, 2009, v. 35, No. 2
A.I. Tovstolytkin, A.M. Pogorily, and D.I. Podyalovskii
|