９Charge-Ordered State in Pr0.65Ca0.35MnO3 Thin Film
Deposited by the Magnetron Sputtering
Osami Yanagisawa*, Masato Arai**, Takanobu Odagiri**,
Takahiro Nakayama** and Mitsuru Izumi**
柳沢
中山

修実*・荒井 雅人**・小田切貴伸**
貴博**・和泉充**

In the Pr0.65Ca0.35MnO3 (PCMO) powder samples, the photo-induced effect is reported in the chargeordered (CO) state associated with the canted antiferromagnetic (CAF) spin order with the electron
spin resonance (ESR) and the powder x-ray diffraction study. The PCMO thin films prepared by theradio frequency magnetron sputtering method were studied focusing on application of this photoinduced effect to industrial application such as the optical-magnetic hybrid device. Better texture of
crystal structure of the thin film is obtained with decreasing the lattice mismatch and the best
substrate is the LaAlO3 (100) substrates. The dR/dT for the PCMO thin film sputtered on SrTiO3(001) for 4 h shows clear sign of the second-order transition at TCO 〜 247 K that gives an evidence forexistence of the CO state. A spontaneous magnetization appears below TCAF 〜 120 K and an
irreversible hysteresis between the FC(C) and ZFC grows remarkably below TCAF with decreasing intemperature. The ESR signal appears below TCAF and splits into at least two signal lines below 80 K.
Both results indicate the existence of magnetic domains with random orientation of ferromagnetic
component in the CAF spin order below TCAF. The ESR profiles for the present PCMO thin film showssome kind of modification with the photo injection (h ＝ 1.17 eV). This result possibly attributeexistence of the mixing of two phase, i.e., the CO - CAF cluster and the photo-induced chargedelocalize (CD) - ferromagnetic (F) cluster.

Keywords : Magnetic materials., Perovskite manganese., Photo-induced effect., Charge-ordered state.,
Canted antiferromagnetic spin order., Magnetron sputtering.
1. INTRODUCTION
The photo-induced effect is reported in the distorted perovskite manganese, Pr0.65Ca0.35MnO3 (PCMO)
powder sample in the charge-ordered (CO) state
associated with the canted antiferromagnetic (CAF)
spin order with the photo injection by near-infrared
Nd YAG laser with photon energy h ＝ 1.17 eV withthe electron spin resonance (ESR) and the x-ray
diffraction study[1, 2, 3]. The photo-induced phenomenonon the charge, spin and orbital strong correlate system
recently has been attracted great interest because not
only academic interests but also industrial opticalapplications. The Pr1−xCaxMnO3 exhibit a magnetic
field induced insulator-metal (I-M) transitions where
the conductivity and magnetization change dramati-cally, an effect termed colossal magnetoresistance(CMR)[4, 5, 6, 7]. The I-M transitions in the manganese
can be achieved not only by the magnetic field, butalso by other external field or stimulation. In thePr1−xCaxMnO3, an electrical current implied by static
electric field triggers the antiferromagnetic insulator(AFI) - ferromagnetic metal (FM) transition at low
temperature[8]. The AFI - FM transition can also be
induced by a synchrotron x-ray illumination at a lowtemperature (＜ 40 K) which is accompanied by asignificant change in the lattice structure and which
can be reversed by thermal cycling[9]. The trace of thecollapse of the CO state was studied by the observation of a photo-current under the action of both anapplied electric field and a pulse of laser irradiation ofphoton energy h ＝ 1.2 eV[10].

＊Maritime Technology Department, Yuge National College of Maritime Technology.
平成１４年９月３０日受理＊＊Laboratory of Applied Physics, Tokyo University of Mercantile Marine.（東京商船大）

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弓削商船高等専門学校 紀要 第２５号（平成１５年）

This photo-induced effect has a grate potentiality
in the industrial application for the optical-magnetic
hybrid device, with which one can control the electric
property by the photo injection and/or the magnetic
field. The fabrication of the thin film provides theadvantages to the industrial application. The firstreason is its ability to enhance the sensitivity of thephoto-induced effect found in the powder sample
against the small penetration depth of the laser light.
The second is its ability to process the large integrated
circuit (LSI) with the usual micro-processing technology for the semiconductor LSI.
However, the phenomenon of oxygen semiconductor in the thin films varies in the preparatory condition and influences the charge carrier concentration as
well as electrical properties like most of the metaloxides. A strain effect due to the lattice mismatch
between the film and the substrate plays an importantrole resulting in a distortion of perovskite structure ofmanganite and eventually in the population of Mn3＋
and Mn4＋ ions. The PCMO thin films on the SrTiO3(100) single crystal substrates prepared by the wet
chemical method so-called sol-gel method does notshow the photo-induced effect or the CO state which
has important role for the photo-induced effect andshow different physical properties form the PCMO
powder samples[11, 12]. The radio frequency magnetron
sputtering is known as a method which can give a thinfilm composition equal to that of the target[13, 14].
In the present communication, the PCMO thinfilms prepared by the radio frequency magnetron
sputtering method were studied focusing on application of the photo-induced effect observed in the PCMO
powder sample to industrial application such as the
optical-magnetic hybrid device. Influence of the strain
effect and the film thickness on structure, transportand magnetic properties of the deposited thin films
were investigated. Physical properties of the PCMO
thin films and the PCMO powder sample werecompared focusing on the existence of the photoinduced effect, the CO state and the CAF spin order.
2. EXPERIMENTThe powder samples of Pr0.65Ca0.35MnO3 were carefully prepared by calcining the mixture of prescribedamount of manganese and calcium carbonates andpraseodymium oxide in the air at 1400 ℃ using theusual ceramic technique. The synthesized powder
sample was pressed and made into a ceramic pellet

with 5 mm thickness and 1.3 inch diameter for a
sputtering target.
The Pr0.65Ca0.35MnO3 thin films were deposited by
the radio frequency magnetron sputtering system(PGS5 : R.S.T. Inc., Japan) equipped with a sputtering source, a substrates holder and in-axis geometry.
The PCMO ceramic pellet was mounted on the radio
frequency magnetron sputtering source, Mak130-V
with the Ne / Fe B magnet, the radio frequency of
13.56 MHz equipped with an auto frequency matchingunit and the max power up to 150 W. The radio
frequency discharge power was set at 100 W. The
SrTiO3 (100) single crystal (STO), LaAlO3 (100) (LAO)
and MgO (100) (MGO) with 10 × 10 × 0.5 mm in size
were used as a substrate to investigate influence ofthe strain effect in physical property of the thin film.
The substrate was mounted on the substrates holder,
SU200CU FK equipped with an electric heater and athermometer with temperature controlling unit andthe max temperature up to 850 ℃. Distance between
the substrate and the target was set at 50 mm. The
in-axis geometry where the target axis and thesubstrates axis are parallel was used. The film deposition was carried out in a chamber with a gas
mixture of argon and oxygen with 1 : 1 in totalpressure with pressure of 4 × 10−2 Torr after vacuum
up to 1 × 10−10 Torr with a turbojet vacuum pump.
The substrate was set at several temperature, 650 ℃,
750 ℃, 800 ℃, 850 ℃ to investigate influence of thedeposition temperature in physical property of the thinfilm. The thin films were deposited for 2 h and 4 h toinvestigate influence of the film thickness in physicalproperty of the thin film. After the radio frequency
discharge was switched off, a chamber was filled withoxygen gas immediately and then slowly cooled down
up to room temperature. The crystallization for thedeposited thin films were done by annealing under O2
gas flow at 1000 ℃ for 10 h.
The structure of the deposited thin films wasinvestigated by the X-ray diffraction at room temperature. Data were collected using X-ray diffractometer(RAD-2A : Rigaku Co. Ltd., Japan) with Cu Ka
radiation (λ ＝ 1.5418 A) equipped with a rotating
anode generator operated at 36.5 mV and 18.5 mA.
The 2 − step scan was used with step width ∆ ＝0.01°− 0.02°, accumulation time 10 s − 100 s/step.
The temperature dependence of the d.c. resistance
was measured by a conventional four-probe methodfrom 290 K to 5 K in the warming run after cooling up
to 5 K using a liq. He closed-cycle type cryostat. The

Charge-Ordered State in Pr0.65Ca0.35MnO3 Thin Film
Deposited by the Magnetron Sputtering（柳沢・荒井・小田切・中山・和泉）

Fig. 1 (a)Fig. 1 (b)１１d.c. magnetization was measured under the magnetic
field 0.01 T which is perpendicular to the c-axis of thinfilm by a SQUID magnetometer (7T-MPMS : Quantum Design, USA) in the warming run after fieldcooling run (FC(W)), the cooling run after field coolingrun (FC(C)) and the zero field cooling run (ZFC). In
the zero field cooling run (ZFC), measurements were
performed after sample was cooled down to a prescribed temperature under zero field, then a field wasraised to 0.01 T.
The ESR measurement for the electron spin on
3＋
Mn and Mn4＋ ionic sites in the PCMO thin film wasdone using the X-band spectrometer (JES-RE1X :JEOL, Japan) operated at 9.0 GHz with a 100 kHz
field modulation. The static magnetic field H0 was
applied to the thin film perpendicular to the c-axis ofthin film. The resonance absorption of the ESR
measurement was observed as a derivative signal
curve. The sample was mounted in a liq. He continuous-flow type cryostat and was cooled from 300 K
down to 10 K. The Mn2＋ diluted in MgO wasemployed for a reference. To investigate a photoinduced effect, a cw Nd-YAG laser with unique photon

Fig. 1 (c)Figure 1 X-ray diffraction profiles at room temperature of the Pr0.7Ca0.3MnO3 (PCMO) thin film sputtered at thedeposition temperature ＝ 650 ℃, 750 ℃, 800 ℃, 850 ℃ on the SrTiO3 (100) single crystal substrates(STO) (a), LaAlO3 (100) (LAO) (b), and MgO (100) (MGO) (c) with annealing process at 1000 ℃ in O2
gas. In addition, the diffraction line from the STO substrate (a), LAO (b), and MGO (c) are also shownwith solid lines.

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弓削商船高等専門学校 紀要 第２５号（平成１５年）

The X-ray powder analysis indicated that the
PCMO powder sample is in single phase with thedistorted perovskite structure and orthorhombic symmetry with the space group Pbnm with lattice
constants a ＝ 5.428 A, b ＝ 5.455 A and c ＝ 7.663 A,

respectively at room temperature.
The detailed
discussion based on the refined structural and atomic
parameters was reported elsewhere[15].
Figure 1 shows the X-ray diffraction profiles atroom temperature of the PCMO thin film sputtered at
the deposition temperature ＝ 650 ℃, 750 ℃, 800 ℃,
850 ℃ on the STO (100) single crystal substrates (a),LAO (100) (b), and MGO (100) (c) with the annealingaround the [040] and [200] diffraction line from the
PCMO. In addition, the diffraction line from the STO
substrate [020] (a), LAO [020] (b), and MGO (c) arealso shown with solid lines. The strong [00n] reflection was observed. Less absence of the peaks fromother orientations. Better texture of crystal structureof the thin film was obtained with increasing thedeposition temperature and the best deposition temperature is 850 ℃[16, 17]. The lattice mismatch between
the PCMO film and the substrate are 1.9 %, 1.0 % and
9.9 % for the STO (100) single crystal substrates, LAO(100), and MGO (100), respectively. The peak intensity of the [040] and [002] diffraction line from the
PCMO thin film increase and the peak intensity form

Fig. 2 (a)Fig. 2 (b)energy h ＝ 1.17 eV were employed for the photo
injection. The laser light was introduced into thesample situated in a cavity resonator through a double
shielded quartz tubes belonging to the continuous flow
He cryostat. The laser power was 175 mW which isequivalent to the injection of 9 × 1017 photons/sec. The
laser spot size was about 1 mm2. The penetration
depth of the laser light is estimated to be about 0.2
mm for the present sample. The ESR measurement
was done under the sequence in which we measure
the ESR without the photo injection, then with thephoto injection and finally without the photo injection
again in turn to check if any kinds of damage to thesample occur.
3. RESULTS AND DISCUSSION

Figure 2 The temperature dependence of the differential resistance (dR/dT) of the Pr0.7Ca0.3MnO3 (PCMO) thinfilm sputtered at the deposition temperature 850 ℃ on the SrTiO3 (100) substrates (STO) for 2 h (a) and4 h (b) with the annealing in the cooling run.

Charge-Ordered State in Pr0.65Ca0.35MnO3 Thin Film
Deposited by the Magnetron Sputtering（柳沢・荒井・小田切・中山・和泉）

１３other orientations decrease prominently decreasing thelattice mismatch. Better texture of crystal structure of
the thin film was obtained with decreasing the latticemismatch and the best substrate is the LAO (100)single crystal substrates. The annealing decrease theoxygen stoichiometry and enhance the crystallizationfrom polycrystal to single crystal[16, 17]. The well-definedorientation of the-axis is confirmed on the STO (100)substrates and LAO (100), according to the X-ray
diffraction. Thickness of the thin films sputtered 2 h
and 4 h were determined as 4000 A and 8000 A
respectively by a laser microscope.
The temperature dependence of the differential
resistance (dR/dT) of the PCMO powder sample shows
a prominent perk at TCO 〜 215 K. This is evident due
to the second-order phase transition associated withformation of the CO state where the charge islocalized on Mn ionic site together with the Mn3＋ and
Mn4＋ alternation leading to the superlattice x-rayreflection[2]. Figure 2 shows the dR/dT of the PCMO
thin film sputtered at deposition temperature 850 ℃
on the STO (100) substrates for 2 h (a) and 4 h (b)with the annealing. The dR/dT of the PCMO thin film

sputtered for 2 h (a) does not show any clear sign ofthe second-order transition associated with CO state.
It is worth to note that there is also no any clear signof the second-order transition in the dR/dT of the
PCMO thin films prepared by the Sol-Gel method[11, 12].
On the contrary, The dR/dT of the PCMO thin film
sputtered for 4 h (b) shows clear sign of the secondorder transition at TCO 〜 247 K that gives an evidence
for the existence of the CO state. The high TCO allows
us to provide photo-magnetic functional devices operated near room temperature. This increase of TCO may
attribute to the deviation from nominal composition
and / or the oxygen deficiency. In the PCMO thin film
sputtered for 4 h whose thickness is estimate as 8000
A, the strain effect is completely relaxed.
Figure 3 shows the d.c. magnetization as afunction of temperature in the PCMO thin film
sputtered at deposition temperature 850 ℃ on the
STO (100) substrates for 2 h (a) and 4 h (b) with theannealing under the magnetic field 0.01 T which isperpendicular to the c-axis of thin film. A spontaneous magnetization appears below TCAF 〜 120 K whichshift lower temperature compared with the PCMO

Fig. 3 (a)Fig. 3 (b)Figure 3 The d.c. magnetization as a function of temperature in the Pr0.7Ca0.3MnO3 (PCMO) thin film sputtered at
deposition temperature 850 ℃ on the SrTiO3 (100) substrates (STO) for 2 h (a) and 4 h (b) with theannealing under the magnetic field 0.01 T which is perpendicular to the c-axis of thin film. FC(C) and
ZFC denote - the magnetization in the cooling run and the warming run after zero field cooling,respectively.

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弓削商船高等専門学校 紀要 第２５号（平成１５年）

powder sample. The irreversible hysteresis between
the FC(C) and ZFC grows remarkably TCAF withdecreasing temperature. The d.c. magnetization in FC(C) shows positive magnetization. On the contrary,
the d.c. magnetization in ZFC shows negative magnetization, in other word, a magnetic pole inversion.
This transition is attributed to the CAF transition.
The present results indicate the existence of magnetic
domains with random orientation of ferromagnetic
component in the CAF spin order below TCAF.
Figure 4 shows the ESR profiles for the PCMO
thin film sputtered at deposition temperature 850 ℃
on the STO (100) substrates for 4 h with the annealing
without the photon injection (dark). Several sharp
dips between 300 mT and 330 mT in the ESR profiles
are coming from the Mn2＋ as a reference. The ESR

signal appears below TCAF 〜 120 K which is good
agreement with the appearance of spontaneous magnetization in d.c. magnetization in FC(C). The ESR
signal splits into at least two signal lines below 80 K.
The center resonance magnetic field of the lower-fieldresonance line shifts to lower magnetic field withdecreasing temperature below 80 K. On the contrary,
the center resonance magnetic field of the higher-fieldresonance line shifts to higher magnetic field withdecreasing temperature below 50 K which corresponds
to decrease of the d.c. magnetization in FC(C). The
present results indicate the existence of magnetic
domains. The ESR profiles for the present PCMO thinfilm shows some kind of modification with the photo
injection (h ＝ 1.17 eV). This result possibly attribute existence of the mixing of two phase, i.e., the CO CAF cluster and the photo-induced charge - delocalize- ferromagnetic cluster.
The electrical and magnetic properties of thin film
and powder samples of PCMO are quite different as
we mentioned above. The difference may be due tothe oxygen stoichiometry, the degree of order of the
population of Mn ions, the charge carrier concentration and eventually electron hopping like in mostmetal oxide materials. A strain effect due to the lattice mismatch between the film and the substrate isplausible and it may control the distortion of perovskite structure.



4. SUMMARY

Figure 4 The ESR profiles for the Pr0.7Ca0.3MnO3(PCMO) thin film sputtered at deposition
temperature 850 ℃ on the SrTiO3 (100)substrates (STO) for 4 h with the annealing
without the photon injection (dark). The
static magnetic field H0 was applied perpendicular to the c-axis of thin film.

The PCMO thin films prepared by the radio
frequency magnetron sputtering method were studiedcompared to the PCMO powder sample focusing on
optimization of the photo-induced effect, the CO state
and the CAF spin order. Better texture of crystal
structure of the thin film is obtained with decreasing
the lattice mismatch and the best substrate is theLAO (100) substrates. The dR/dT of the PCMO thinfilm sputtered on STO (001) for 4 h (b) shows clear
sign of the second-order transition at TCO 〜 247 K thatgives an evidence for existence of the CO state. A
spontaneous magnetization appears below TCAF 〜 120
K and an irreversible hysteresis between the FC(C)and ZFC grows remarkably below TCAF with decreasing
temperature. The ESR signal appears below TCAF andsplits into at least two signal lines below 80 K. Bothresults indicate the existence of magnetic domains
with random orientation of ferromagnetic component
in the CAF spin order below TCAF. The ESR profiles

Charge-Ordered State in Pr0.65Ca0.35MnO3 Thin Film
Deposited by the Magnetron Sputtering（柳沢・荒井・小田切・中山・和泉）

for the present PCMO thin film shows some kind of
modification with the photo injection (h ＝ 1.17 eV).
This results possibly attribute existence of the mixingof two phase, i.e., the CO - CAF cluster and the photoinduced charge - delocalize - ferromagnetic cluster.



5. ACKNOWLEDGMENTS
This study has been supported by the Science andTechnology Research Grant from Ministry of Education, Culture, Science and Technology in Japanthrough grant No. Youth B 14750562 and Sprout
13875121. The authors thank the Materials Design
and Characterization Laboratory, Institute of Solid
State Physics, University of Tokyo for the d.c. magnetization measurement facilities.
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