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Physical property of Pr0.65Ca0.35MnO3 thin film
deposited by the radio frequency magnetron sputtering
Osami Yanagisawa*, Mitsuru Izumi**, Takahiro Nakayama**,
Masato Arai** and Yi Shen**
A photo-induced effect in Pr0.65Ca0.35MnO3 (PCMO) powder sample is reported with the electron
paramagnetic resonance (EPR) and the x-ray diffraction study. This photo-induced effect occurs in the
charge-ordered (CO) state associated with the canted antiferromagnetic (AF) spin order. The PCMO
thin films prepared by a radio frequency magnetron sputtering method on the SrTiO3 (100) single
crystal were studied compared to the powder sample focusing on the optimization of the photo-induced
effect. An annealing process at 1000 ℃ in O2 gas decreases the oxygen stoichiometry and enhances
the crystallization. Better texture of crystal structure of the thin film can obtain with higher
deposition temperature. The best deposition temperature is 850 ℃. The present PCMO thin films
have different physical property. The dR/dT of the PCMO thin film does not show clear sign of theonset of the second-order CO transition. A spontaneous magnetization appears below 70 K. The
irreversible hysteresis between the FC(C) and ZFC grows with a decrease in temperature remarkably
below 55 K which is shifted lower temperature compared with the powder sample.
PACS Nrs. : 72.80.Ga, 75.25.＋z, 76.30.−v, 71.38.＋i
Keywords : Magnetic materials., Oxides., Colossal magnetoresistance., Photo-induced effect., Chargeordered state., Radio frequency magnetron sputtering.
1. INTRODUCTION
The photo-induced phenomenon on charge, spinand orbital strong correlate system recently has been
attracted great interest because not only academic
interests but also industrial optical applications. Oneof well known systems is the distorted perovskite
manganese, R1−xAxMnO3 (R is trivalent rare earth
element and A is divalent alkaline earth element) withsmall ionic radii of (A, R) site ion. The Pr1−xCaxMnO3
exhibits a magnetic field induced insulator-metal (I-M)
transitions where conductivity and magnetization
change dramatically, an effect termed colossal magnetoresistance (CMR) [1 2 3 4]. The I-M transitions in the
manganese can be achieved not only by a magnetic
field, but also by other external field or stimulation. In
the Pr1−xCaxMnO3, an electrical current implied bystatic electric field triggers an antiferromagnetic
insulator (AFI) - ferromagnetic metal (FM) transition
at low temperature[5]. The AFI-FM transition can also
be induced by a synchrotron x-ray illumination at low
temperature (＜40 K). This AFI-FM transition is ac-

companied by a significant change in the lattice
structure and reversed by thermal cycling[6]. The traceof the collapse of a charge-ordered (CO) state wasstudied by the observation of a photo-current under
the action of both an applied electric field and a pulseof laser irradiation of photon energy hυ ＝ 1.2 eV[7]. We
have reported the different aspects of the photoinduced effect on the electron paramagnetic resonance(EPR) and the x-ray diffraction in Pr0.65Ca0.35MnO3(PCMO) powder sample under near-infrared laser
irradiation of photon energy hυ ＝ 1.17 eV[8 9 10]. The
results give an evidence for the photo-induced collapseof the CO state.
Such anomalous physical properties are explainedby the ground state of the R1−xAxMnO3 which ischaracterized by a competing interaction between two
different ground states : one is a charge-delocalized(CD) metal state with the ferromagnetic (F) spin orderand relatively small Jahn-Teller (JT) distortions andthe other is the CO insulating state with theantiferromagnetic (AF) spin order. In the CD state,
the ferromagnetic (F) metal itself has been clarified in＊Maritime Technology Department, Yuge National College of Maritime Technology.
＊＊Laboratory of Applied Physics, Tokyo University of Mercantile Marine.

平成１３年９月２８日受理２弓削商船高等専門学校 紀要 第２４号（平成１４年）

the double-exchange interaction scheme[11 12 13], in which
the doped holes at eg orbital in Mn4＋ site exhibit akind of hopping conduction associated with thepolarized spins for both Mn4＋ and Mn3＋ sites. On theother hand, the CO state is characterized as an antiferromagnetic (AF) spin order on Mn ions, and the
Mn3＋ sublattice retains a cooperative JT distortion,
thereby giving rise to an combination of charge,
orbital, and magnetic ordering. Upon heating, both
the CO and the CD states transform into a chargelocalized paramagnetic insulator (PI) phase, characterized by semiconducting properties. The switching in d.
c. resistivity between the CO state and the CD state, I-M transition, can be achieved by the external field or
stimulation.
This photo-induced effect has a great 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 a 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 themetal oxides. A strain effect due to the latticemismatch between the film and the substrate plays animportant role resulting in a distortion of perovskite
structure of manganite and eventually in the population of Mn3＋ and Mn4＋ ions. The PCMO thin films on
the SrTiO3 (100) single crystal substrates prepared by
the sol-gel method do not show the photo-induced
effect or the CO state which has important role for thephoto-induced effect and show different physicalproperties form the PCMO powder samples[14 15]. The
radio frequency magnetron sputtering is known as amethod which can give a thin film composition equal
to that of the target[16 17].
In the present communication, the radio frequency
magnetron sputtering method has been employed toprepare the PCMO thin films on the STO (100) single
crystal substrates. Influence of the annealing and thedeposition temperature on structure, transport andmagnetic properties of the deposited thin films were

investigated. Physical properties of the PCMO thinfilms and the PCMO powder sample were comparedfocusing on the existence of the photo-induced effectand the CO state.
2. EXPERIMENTThe powder samples of Pr0.65Ca0.35MnO3 were
carefully prepared by calcining the mixture of prescribed amount of manganese and calcium carbonatesand praseodymium oxide in the air at 1400 ℃ using
the usual 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.
Thin films were deposited by the radio frequency
magnetron sputtering system (PGS5, R.S.T. Inc.,
Japan) equipped with a sputtering sauce with capability up to three sauce, a substrates holder withcapability up to three holder and in-axis geometry
with capability for off-axis. The ceramic pellet was
mounted on the radio frequency magnetron sputtering
sauce, Mak130-V with the Ne/Fe B magnet, the radio
frequency of 13.56 MHz equipped with an auto frequency matching unit and the max power up to 150 W.
Power of 100 W was applied for 2 h. The STO (100)single crystal substrates with 10 × 10 × 0.5 mm insize was used as a substrate. The substrate wasmounted on the substrates holder, SU200CU FK
equipped with an electric heater and a thermometerwith temperature controlling unit and the maximum
temperature up to 850 ℃. Distance between thesubstrate and the target was set at 50 mm. The inaxis geometry where the target axis and the substrates axis are parallel was used. The sputtering ofoxide films should be carried out in environment gas
with higher pressure. Thus, the energy of the harmful
negative ions are decreased by collisions with theplasma particles before their arrival to the substratesurface. The sputtering was carried out in a chamberwith a gas mixture of argon and oxygen with 1 : 1 intotal pressure 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 ℃, 850 ℃ in order to study influence of
deposition temperature in physical property of the thinfilm.
After the radio frequency discharge wasswitched off, a chamber was filled with oxygen gas
immediately and then slowly cooled down to room
temperature. The crystallization for the deposited

Physical property of Pr0.65Ca0.35MnO3 thin film deposited by the radio frequency
magnetron sputtering（柳沢・和泉・中山・荒井・沈）

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thin films was done by annealing under O2 gas flow at
1000 ℃ for 1 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. with Cu K α radiation (λ ＝1.5418 Å) equipped with a rotating anode generator
operated at 36.5 kV and 18.5 mA. The 2θ − θ stepscan was used with step width ∆θ ＝ 0.01°− 0.02°,
accumulation time 10 s − 100 s/step. Thickness ofthe deposited thin films were determined as 4500Å bya laser microscope.
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
d.c. magnetization was measured under the magnetic
field 0.01 T by a SQUID susceptometer in thewarming run after field cooling run (FC(W)), thecooling run after field cooling run (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
the zero magnetic field, then the magnetic field wasraised to 0.01 T.
3. RESULTS AND DISCUSSION
The X-ray powder analysis indicated that the
PCMO powder sample was in single phase with thedistorted perovskite structure and symmetry is orthorhombic with the space group Pbnm with lattice
constants a ＝ 5.428 Å, b ＝ 5.455 Å and c ＝ 7.663Å, respectively at 290 K. The detailed discussion

Figure 1 X-ray Cu-K α diffraction profiles of the Pr0.7
Ca0.3MnO3 (PCMO) thin film sputtered at
deposition temperature ＝ 750 ℃ on the
SrTiO3 (100) single crystal substrates (STO)
with the annealing process at 1000 ℃ in O2
gas at the room temperature.

Figure 2 X-ray Cu-K α diffraction profiles around[001] (a) and [002] (b) of the Pr0.7Ca0.3MnO3(PCMO) thin film sputtered at deposition
temperature ＝ 750 ℃ on the SrTiO3 (100)single crystal substrates (STO) with (＋)
and without (○) annealing process at 1000
℃ in O2 gas at the room temperature. In
addition, the [001] line (a) and the [002]line (b) from the STO substrate are also
shown with (×) mark.

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弓削商船高等専門学校 紀要 第２４号（平成１４年）

based on the refined structural and atomic parameters
was reported elsewhere[18].
Figure 1 shows the X-ray diffraction profiles of the
PCMO thin films sputtered at deposition temperature＝ 750 ℃ on the STO (100) substrates at the room
temperature. The strong [00l] reflection was obseved.
Less absence of the peaks from other orientations.
Figure 2 shows the X-ray diffraction profilearound [001] (a) and [002] (b) of the PCMO thin films
sputtered at deposition temperature ＝ 750 ℃ on the
STO (100) substrates at the room temperature. In
addition, the [001] line (a) and the [002] line (b) fromthe STO substrate are also shown with (×) mark.
Mark with (＋) and (O) show the PCMO thin films
with and without the annealing process at 1000 ℃ in
O2 gas. The peak intensity of the X-ray diffraction
from [001] and [002] of the PCMO thin film increases
and peak intensity from other orientations decreaseprominently after the annealing process. The annealing process decrease the oxygen stoichiometry andenhance the crystallization from polycrystal to single
crystal.

Figure 3 X-ray Cu-K α diffraction profiles around[002] of the Pr0.7Ca0.3MnO3 (PCMO) thin film
sputtered at deposition temperatures ＝
650 ℃ (×), 750 ℃ (＋), 850 ℃ (△) on the
SrTiO3 (100) substrates (STO) with theannealing process at 1000 ℃ in O2 gas at
the room temperature.

Figure 4 (a) Temperature dependence of the differential resistance (dR/dT) of the Pr0.65Ca0.35MnO3(PCMO) powder sample. (b) Temperaturedependence of the differential resistance (dR/dT) of the PCMO thin film sputtered at
deposition temperature ＝ 800 ℃ on the
SrTiO3 (100) substrates (STO) with theannealing.

Physical property of Pr0.65Ca0.35MnO3 thin film deposited by the radio frequency
magnetron sputtering（柳沢・和泉・中山・荒井・沈）

Figure 3 shows the X-ray diffraction profiles
around [002] of the PCMO thin films on the STO (100)substrates with the annealing process at 1000 ℃ in O2
gas at the room temperature. Mark with (×), (+) and(△) show the PCMO thin film sputtered at deposition
temperatures, ＝ 650 ℃, 750 ℃, 850 ℃, respectively.
Peak intensity of the X-ray diffraction from [002] of
the PCMO thin film increases prominently withincreasing deposition temperature. Better texture of
crystal structure of the deposited thin film can obtainwith increasing deposition temperature. The best
deposition temperature was 850 ℃.
The electric transport property of the powder
sample and the thin film are significantly different.
Figure 4 (a) shows the temperature dependence of thedifferential resistance (dR/dT) of the PCMO powder
sample. It is the semiconductor-like without themagnetic field at whole temperature range. The dR/dT shows a prominent peak which is evident due tothe second-order phase transition associated withformation of the CO state where the charge islocalized on Mn ionic site at TCO 〜 215 K together
with the Mn3＋ and Mn4＋ alternation leading to the５superlattice x-ray reflection[9]. The powder sample
shows the CMR effect (RM−R0)/R0 〜 400 % with athreshold magnetic field of about 2 T at the CO state
below TCO 〜 215 K.
Figure 4 (b) shows thetemperature dependence of the differential resistance(dR/dT) of the PCMO thin film sputtered at deposition
temperature 800 ℃ on the STO (100) substrates withthe annealing. The dR/dT does not show any clear
sign of the onset of the second-order transition thatgives an evidence for the existence of the CO state.
Figure 5 (a) shows the D.c. magnetization as afunction of temperature in the PCMO powder sample.
A spontaneous magnetization appears below TCAF 〜
125 K. The irreversible hysteresis between the FC(W) and ZFC grows remarkably below TCAF with adecrease in temperature, especially below 115 K. The
present observation is a typical magnetic behavior incase of the existence of spin-glass state[4].
Themagnetic diffuse scattering is observed around thefundamental magnetic Bragg reflection of the parent
spin structure in the neutron diffraction study which
may indicate that the spin-glass type disorder exists inthe system. This diffuse scattering decreases drasti-

Figure 5 (a) D.c. magnetization as a function of temperature in the Pr0.65Ca0.35MnO3 (PCMO) powder sample
under the magnetic field 0.01 T. FC(C), FC(W) and ZFC denote, the magnetization in the cooling run
after field cooling run, the warming run after field cooling run, the warming run after zero fieldcooling, respectively. (b) D.c. magnetization as a function of temperature in the PCMO thin film
sputtered at deposition temperature ＝ 800 ℃ on the SrTiO3 (100) substrates (STO) with the annealing
under the magnetic field 0.01 T.

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弓削商船高等専門学校 紀要 第２４号（平成１４年）

cally by applying a relatively weak magnetic field of 〜
2.0 T, and the component parallel to the field
increases rapidly. Such behavior also support that the
diffuse scattering should be attributed to the spinglass component which is sensitive to the weakexternal magnetic field[1]. In the PCMO, the concentration, x of Mn3＋ ions does not retain a commensurate
such as x ＝ 1/4, 1/3 and 1/2. The observed magnetic
structure in the orthorhombic ab plane is that of thecommensurate value x ＝ 1/2 structure as reported inan early study[19 20]. Thus, the formation of the COstate after CE-type configuration makes excess Mn3＋
ions intersperse randomly over Mn4＋ ion sites. Thenthe onset of some kind of frustrated exchangeinteraction leads to the spin-glass like behavior at the
low temperature as detected by the present ESR
profiles. Figure 5 (b) shows the D.c. magnetization as
a function of temperature in the PCMO thin film
sputtered at deposition temperature ＝ 800 ℃ on the
STO (100) substrates with the annealing under themagnetic field 0.01 T. A spontaneous magnetization
appears below 70 K located below TCAF 〜 125 K of the
PCMO powder sample. The irreversible hysteresis
between the FC (C) and ZFC grows with a decrease intemperature remarkably 55 K which is shifted lower
temperature compared with the powder sample. It
indicates existence of the spin-glass or some kind ofmagnetic order at low temperature.
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 to theoxygen 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 thelattice mismatch between the film and the substrate isplausible and it may control the distortion of perovskite structure.
4. SUMMARY
The PCMO thin films prepared by the radio
frequency magnetron sputtering method on the STO(100) single crystal were studied compared to the
PCMO powder sample focusing on the optimization of
the photo-induced effect. The annealing process at
1000 ℃ in O2 gas decreases the oxygen stoichiometry
and enhance the crystallization. Better texture of thecrystal structure of the deposited thin film can obtainwith higher deposition temperature. The best deposi-tion temperature is 850 ℃. The dR/dT of the PCMO
thin film does not show clear sign of the onset of thesecond-order CO transition. A spontaneous magnetization appears below 70 K. The irreversible hysteresis
between the FC(C) and ZFC grows with a decrease intemperature remarkably 55 K which is shifted lower
temperature compared with the PCMO powder sample. The present PCMO thin film has different
physical property and indicate neither the photoinduced effect nor the CO state.
5. ACKNOWLEDGMENTS
The present study has been supported by the
Sumitomo foundation for fundamental science research through grant No. 990278.
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magnetron sputtering（柳沢・和泉・中山・荒井・沈）

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