Journal of Magnetism and Magnetic Materials 324 (2012) 3863–3869

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Journal of Magnetism and Magnetic Materials
journal homepage: www.elsevier.com/locate/jmmm

Suppression of the low-temperature phase-separated state under pressurein (Eu1  xGdx)0.6Sr0.4MnO3 (x ¼ 0,0:1)
Tasuku Inomata a, Michiaki Matsukawa a,n, Daichi Kimura a, Yoshiaki Yamato a, Satoru Kobayashi a,
Ramanathan Suryanarayanan b, Sigeki Nimori c, Keiichi Koyama d, Kohki Takahashi e, Kazuo Watanabe e,
Norio Kobayashi eaDepartment of Materials Science and Engineering, Iwate University, Morioka 020-8551, Japan
Laboratoire de Physico-Chimie de L’Etat Solide, CNRS, UMR8648 Universite Paris-Sud, 91405 Orsay, FrancecNational Institute for Materials Science, Tsukuba 305-0047, Japand
Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japane
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japanba r t i c l e i n f oabstract

Article history:
Received 17 May 2012
Received in revised form
14 June 2012
Available online 7 July 2012

We have demonstrated the effect of pressure on the steplike metamagnetic transition and its associatedmagnetostriction in (Eu1  xGdx)0.6Sr0.4MnO3 (x ¼ 0 and 0.1). The critical ﬁeld initiating the ﬁeld induced
ferromagnetic transition in both samples is lowered by the applied pressure. The further application of
external pressure up to 1.2 GPa on the x ¼ 0 parent sample causes a spontaneous ferromagnetictransition with a second-order like character, leading to collapses of the steplike transition and its
concomitant lattice striction. These ﬁndings indicate a crucial role of the low-temperature phaseseparated state characterized by a suppressed magnetization upon decreasing temperature.
& 2012 Elsevier B.V. All rights reserved.

Keywords:
Doped manganite
Phase separation
Pressure effect
Steplike transition

1. Introduction
Manganites (RE1  xAExMnO3 ; RE ¼Y, rare earth; AE¼Pb,Ca,Sr,Ba) with perovskite structure have been extensively investigated since the discovery of colossal magnetoresistance (CMR)
effect [1]. The spontaneous insulator to metal transition and its
associated CMR effect are well explained on the basis of the
double exchange (DE) model between Mn3 þ and Mn4 þ ions [2].
Furthermore, the phase separation (PS) model, where the ferromagnetic (FM) metallic and antiferromagnetic charge ordered(AFM-CO) insulating clusters of competing electronic phases
coexist, strongly supports experimental studies of manganites [3].
In a recent study [4] on the bandwidth-temperature-magnetic
ﬁeld phase diagram of RE0.55Sr0.45MnO3 with nearly half doping,
the bandwidth was controlled by chemical substitution andhydrostatic pressure. In particular, near a critical pressure, thecharacter of the ferromagnetic transition varies from the ﬁrst to
second order. The applied pressure gives rise to a larger bandwidth accompanied by a decrease of short range charge/orbital
ordering ﬂuctuations, resulting in weakened ﬁrst order transition.
Several recent researches for metamagnetic transitions of
doped manganites in the phase separated state have revealednCorresponding author.
E-mail address: matsukawa@iwate-u.ac.jp (M. Matsukawa).

0304-8853/$ - see front matter & 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jmmm.2012.06.036

that ultrasharp magnetic transition of Pr0.5Ca0.5Mn0.95Co0.05O3
appears at low temperatures. To account for this phenomenon,a martensitic model based on lattice mismatch between competing CO and FM phases has been proposed [5–7] but questions
have been raised as to the validity of such a scenario [8]. It isbelieved that the martensitic scenario is ruled out since grainboundaries in polycrystalline samples act as ‘‘ﬁre wall’’ against
such a progress of magnetic transition, resulting in a suppressionof its steplike transition. Ghivelder et al. have observed a sudden
temperature rise ð  30 KÞ associated with the steplike magnetictransition of La5/8  xPrxCa3/8MnO3 (x¼0.4), indicating a release oflarge latent heat (or entropy) from low-temperature phaseseparated to FM ordered states. According to their ﬁndings[9,10], after zero-ﬁeld cooling, the manganite system showing
the steplike transition reaches a thermally stable state with asmall, and almost time independent fraction of FM, which isdispersed as isolated regions within a CO matrix. This phaseseparated state is realized at low temperatures by large energy
barriers separating the AFM-CO and FM phases and strains due tothe lattice mismatch between the coexisting phases. Increasing
the temperature under the applied ﬁeld, the system is thentransferred from the equilibrium to non-equilibrium states, promoting a growth of the FM phase over the majority AFM-CO
matrix.
A close relationship of the TH phase diagram with steplike
metamagnetic transition for low band width manganites,

T. Inomata et al. / Journal of Magnetism and Magnetic Materials 324 (2012) 3863–3869

Sm0.55Sr0.45MnO3 and Eu0.58Sr0.42MnO3, has been pointed out in aprevious work [11]. The negative curvature in the temperaturedependence of critical magnetic ﬁeld, dHc =dT o 0, at low temperatures is an essential condition for the magnetic transition
observed in doped manganites, where Hc is a critical ﬁeld causing
the ferromagnetic transition. The FM transition of local region
generates a release of latent heat, which drives its neighborregions of non-FM states to FM ordering state because thetemperature rise at low temperatures gives rise to a lower criticalﬁeld promoting further FM ordering. Furthermore, analysis ofexperimental data on the magnetization step in phase separated
manganites La5/8  xPrxCa3/8MnO3 (x ¼0.40, 0.38, and 0.36) points
to the role of thermal coupling as a key parameter of theinstability in a dynamical system [12].
The Eu1  xSrxMnO3 ðx  0:4 for polycrystalline samples) system
is a spin-glass like insulator at low temperature because thesubstitution of Eu ion with smaller ion radius for La site gives rise
to both narrow band width and an increase in the quencheddisorder [13–15]. It is well known that the former and latterparameters are controlled by the average value and the varianceof the RE/AE ionic radii in RE1  xAExMnO3, respectively [16]. In aprevious work on single crystalline Eu1  xSrxMnO3 ðx  0:5Þ, theCO phase is not formed in a long-range manner due to anincreased quenched disorder.
In this paper, to examine the steplike metamagnetic transition andits associated lattice change in the phase separated manganite, we
demonstrate the effect of pressure on both the isothermal magnetization and magnetostriction in (Eu1 xGdx)0.6Sr0.4MnO3 (x¼0 and 0.1).
In Section 2, the experimental outline is described. In Section 3, themagnetization and magnetostriction data under pressure are shownwith X-ray diffraction measurement on the parent sample undermagnetic ﬁeld. Section 4 is devoted to the discussion followed by theﬁnal section of summary.

3. Results
3.1. Magnetization
First of all, let us show in Fig. 1 the temperature variation of
the zero ﬁeld cooled (ZFC) magnetization of (Eu,Gd)0.6Sr0.4MnO3under ambient and applied pressures. The critical ﬁeld Hc at thecorresponding temperatures is determined from the inﬂection
points in isothermal magnetization curve upon increasing theapplied ﬁeld up to 5 T as shown in the inset of Fig. 1. The negative
curvature in dHc =dT at low temperatures is an essential condition
for the appearance of the steplike magnetic transition as discussed in Refs. [6,11]. As displayed in Fig. 1(a), the ZFC magnetization curve shows a PM to FM transition near 60 K followed bya plateau, upon decreasing T, it then decreases rapidly untilT  20 K, and ﬁnally remains a lower value down to 5 K. We
expect that the rapid suppression of magnetization observed at
low temperatures is caused by a magnetic frustration between
double-exchange and super-exchange interactions.
The application of hydrostatic pressure on the ZFC magnetization causes an enlargement of the FM region, limiting a lower
magnetization region below 10 K. A volume fraction of the FMphase under pressure is estimated to be almost 97% at the100
80
M (emu/g)

3864

60
40
20

0GPa
0.8GPa1.2GPa

2. Experiment

0

0

50

100
150
Temperature (K)

200

100
150
Temperature (K)

200

100
80
M (emu/g)

Polycrystalline samples of (Eu1  xGdx)0.6Sr0.4MnO3 ðx ¼ 0,0:1Þ
were prepared with a solid-state reaction method. The stoichiometric mixtures of Eu2O3, Gd2O3, SrCO3, and Mn3O4 high purity
powders were calcined in air at 1000 1C for 24 h and 1250 1C for
48 h. The products were then ground and pressed into cylindricalpellets. The pellets were ﬁnally sintered at 1350 1C for 36 h. X-ray
diffraction data revealed that all samples are almost single phasewith orthorhombic structures ðPbnmÞ. The lattice parameters of
the parent sample (x ¼0) are a ¼5.4424 Å, b¼5.4329 Å, andc¼7.664 Å, which is in fair agreement with a previous work[13]. X-ray powder diffraction (XRD) measurements under highﬁelds up to 4 T at low temperatures were performed with Cu K aradiation at the High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University [17]. In
particular, the XRD data at 581 r 2y r721 were taken with a step
size of 0.0021.
The electrical resistivity was measured with a four-probe
method. The magnetization measurement was carried out using
commercial superconducting quantum interference device(SQUID) magnetometers both at Iwate Univ. and National Institute for Materials Science. Hydrostatic pressures in magnetizationand magnetostriction measurements were applied by using aclamp-type CuBe cell up to 1.2 GPa. Fluorinert was used as apressure transmitting medium. The magnitude of pressure wascalibrated by the pressure dependence of the critical temperatureof lead. Magnetostriction was measured by using a superconducting magnet at the High Field Laboratory for Superconducting
Materials, Institute for Materials Research, Tohoku University.

60
40
20
0

0GPa
0.8GPa1.2GPa050

Fig. 1. (a) Temperature variation of the zero ﬁeld cooled (ZFC) magnetization of
the Eu0.6Sr0.4MnO3 bulk sample under 0 GPa, 0.8 GPa, and 1.2 GPa. The TH phase
diagram of the parent sample is established from isothermal magnetization data
after zero ﬁeld cooling at selected temperatures as shown in the inset. The appliedﬁeld is adjusted not to attain a critical ﬁeld corresponding to the occurrence of a
steplike behavior except for the 1.2 GPa data. Ha ¼ 1:5 T at 0 GPa, and 1 T both at
0.8 and 1.2 GPa. (b) ZFC magnetization curves of the (Eu0.9Gd0.1)0.6Sr0.4MnO3 bulk
sample under 0 GPa, 0.8 GPa, and 1.2 GPa. Ha ¼ 3 T at 0 GPa, 1.5 T at 0.8 GPa, and1 T at 1.2 GPa. For comparison, the critical ﬁeld versus temperature boundary isplotted as a function of the applied pressure in the inset.

T. Inomata et al. / Journal of Magnetism and Magnetic Materials 324 (2012) 3863–3869

curve. The magnitude of the magnetization is not saturated even at
the maximum ﬁeld of 5 T. The application of external pressure on the
Gd10% sample lowers the switching ﬁeld for occurrence of stepliketransition as depicted in Fig. 3. At a lowest temperature of 2 K, amulti-steplike transition occurs under the applied pressures of
0.8 and 1.2 GPa. A second step observed around 3 T under 0.8 GPa
is suppressed under the application of higher pressure of 1.2 GPa
associated with an enhanced ﬁrst steplike transition, but a tiny
steplike variation remains. This trend is very similar to the MH curveof polycrystalline Pr0.5Ca0.5Mn0.97Ga0.03O3 with two abrupt magnetization jumps followed by plateaus [18].

We attempt to measure the corresponding magnetostrictiondLðHÞ=Lð0Þ of the parent Eu0.6Sr0.4MnO3 under ambient pressure atselected temperatures of 4 K, 8 K, and 20 K after zero ﬁeld cooling(Fig. 4). For comparison, the dLðHÞ=Lð0Þ data of the Gd doped
sample are presented. We note that the magnitude of volume
magnetostriction dLðHÞ=Lð0Þ ¼  4  104 at high ﬁelds isalmost independent on the direction of applied ﬁeld (not shownhere). The value of dLðHÞ=Lð0Þ associated with the ﬁeld induced
FM metal transition is in good agreement with the previous dataof Eu0.55Sr0.45MnO3 [19]. The steplike magnetostriction isobserved upon raising the magnetic ﬁeld, accompanied by the
steplike metamagnetic transition. A spiky variation observed indLðHÞ=L beyond  4  104 is not real one, which originatesfrom by an apparent change in the resistance of strain gauge itself
due to a rapid release of latent heat associated with the ﬁeld
induced steplike transition [8]. We roughly estimate the apparent
decrease in the resistance of the strain gauge to be  0:08% at
4.2 K, giving a sudden temperature rise of the sample above about

100

100

80

80

60
40

0

0

1

2
H (T)

40

0

4

3

60

100

100

80

80

60
40
0GPa
0.8GPa1.2GPa

20
0

0

1

2
H (T)

3

0GPa
0.8GPa1.2GPa20

0GPa
1.2GPaM (emu/g)

M (emu/g)

3.2. Magnetostriction

M (emu/g)

M (emu/g)

intermediate temperatures. For further applied pressure of
1.2 GPa, a lower magnetization region disappears and instead ofit the FM phase still remains down to 4 K, indicating no stepliketransition of the Eu based sample. Moreover, we attempt tomeasure the ZFC magnetization curve of the Gd substituted
sample, to examine the inﬂuence of chemical pressure on themagnetic properties. For comparison, the critical ﬁeld versus
temperature boundary is plotted as a function of the appliedpressure in the inset of Fig. 1(b). We note that the HT phaseboundary line of the Gd10% sample under 0.8 GPa is similar tothat of the parent sample at ambient pressure.
Next, to further examine the inﬂuence of lattice on themagnetic property of the bulk Eu0.6Sr0.4MnO3, we attempt tomeasure the low-temperature magnetization as a function of ﬁeld
up to 5 T under ambient and applied pressures. At low temperatures, the steplike magnetic transition appears just around 2.6 T
upon increasing the applied ﬁeld as shown in Fig. 2. The application of external pressure on the magnetization depresses theswitching ﬁeld for the steplike transition from 2.6 T at 0 GPa
down to  1:2 T at 0.8 GPa. Furthermore, the ultrasharp phasetransition to the FM state disappears under an applied pressure of
1.2 GPa accompanied by a rapid suppression of magnetic hysteresis. This ﬁnding is well consistent with the low temperature MT
curve showing no suppressed magnetic state.
To elucidate a close relationship between the lattice and spin
coupling in the Gd substituted sample, we try to measure the effect ofpressure on the magnetization curve of (Eu0.9Gd0.1)0.6Sr0.4MnO3. Uponlowering temperature down to 4 K, a steplike magnetic transition
appears around 4.2 T under ambient pressure as shown in Fig. 3(c). At
5 K, an abrupt transition observed at the parent sample is smeared toa continuous variation of the MH curve for the Gd10% sample(Fig. 3(d)). The critical ﬁeld corresponding to the metamagnetictransition is determined to be 4.8 T from the inﬂection of the MH

20

3865

0

1

2
H (T)

60
40
0GPa
0.8GPa1.2GPa

20

4

4

3

0

0

1

2
H (T)

3

4

Fig. 2. Isothermal magnetization of the Eu0.6Sr0.4MnO3 bulk sample measured under ambient pressure and hydrostatic pressures at (a) 2 K, (b) 3 K, (c) 5 K, and (d) 8 K, after
zero ﬁeld cooling down to selected temperatures. For each measurement, a magnetic ﬁeld is applied up to a maximum ﬁeld at the sweep rate of 0.2 T/step.

T. Inomata et al. / Journal of Magnetism and Magnetic Materials 324 (2012) 3863–3869

100

100

80

80
M (emu/g)

M (emu/g)

3866

60
40
0GPa
0.8GPa1.2GPa

20
0

0

1

2

3

4

60
40
0GPa
0.8GPa1.2GPa

20
0

5

0

1

2

3

4

5

H (T)

H (T)
100
80
M (emu/g)

M (emu/g)

80
60
40
0GPa
0.8GPa1.2GPa

20
0

0

1

2

3

4

H (T)

60
40
20

5

0

0GPa
0.8GPa1.2GPa

0

1

2

3

4

5

H (T)

Fig. 3. Isothermal magnetization of the Gd substituted Eu0.6Sr0.4MnO3 bulk sample taken under 0 GPa, 0.8 GPa, and 1.2 GPa, after the sample was zero ﬁeld cooled down to
the desired temperatures of (a) 2 K, (b) 3 K, (c) 4 K, and (d) 5 K. The sweep rate is set to be 0.2 T/step up to 5 T.

dT  20 K, which is not very far from the value reported by
Ghivelder et al. [6] For the Gd substituted sample, the magnetostriction dLðHÞ=L also corresponds to the MH curve at 5 K.
To check the effect of magnetic ﬁeld on lattice parameters, we
carry out X-ray diffraction measurements of the parent sample
under magnetic ﬁelds up to 4 T at 10 K as shown in Fig. 5. Our
X-ray powder diffraction data show no structural phase transition
associated with the ﬁeld induced magnetic transition of theparent sample. Instead, the ﬁeld dependence of the peak proﬁlesin Fig. 5 reveals a stable decrease of the lattice parameters uponincreasing applied ﬁelds. Applying the Bragg equation to thepresent data and differentiating it with respect to diffraction
angle, we obtain a relationship that the average lattice variation
Da0 =a0 is proportional tothe peak shift Dy in 2y scan. Here, we
pﬃﬃﬃ
assume that a  b  c= 2 ¼ a0 . In an applied ﬁeld of H ¼4 T,
Da0 ðHÞ=a0 ð0Þ reach 2:3  104 and 3:4  104 , for the peakshifts towards higher angle near 2y ¼ 601 and 701, respectively, as
presented in Fig. 5(b) and (c). These ﬁndings qualitatively agreewith the magnetostriction behavior of dLðHÞ=L of Fig. 4.
Fig. 6 shows the effect of external pressure on the magnetostriction of the parent sample which is well consistent with that on
the isothermal magnetization. In particular, the value of dLðHÞ=L
under an application of 1.2 GPa remains almost zero uponincreasing the applied ﬁeld up to 7 T and exhibits no magnetic
hysteresis, indicating a spontaneous transition of the system tothe ferromagnetic state before the application of a magnetic ﬁeld.
Our data are in fairly agreement with the previous results that anegative magnetovolume effect disappears above 1.15 GPa [20].

4. Discussion
First of all, the temperature dependence of the magnetizationof both parent and Gd10% samples under ambient and appliedpressures, except for the high pressure data of the parent sample,
is strongly suppressed at low temperatures, where is characterized by the phase separation state. On the other hand, the further
application of pressure up to 1.2 GPa on the parent one causes acollapse of the low temperature PS state associated with asuppressed magnetization, resulting in the disappearance of the
steplike transition. The application of the external pressure on
both samples lowers the critical ﬁeld for the FM transition but
does not change the negative curvature in the HT phase diagram,dHc =dT o0. Accordingly, it is concluded from our ﬁndings that the
low-temperature phase separated state and its related negative
temperature dependence of Hc(T) are essential condition for theappearance of the steplike magnetic transition. Further, for theparent sample, we observe that the ferromagnetic component
enhanced by the applied pressure of 0.8 GPa is reduced under
1.2 GPa accompanied by the broadening of the FM transition
width around Tc. As for the unusual feature in the MT curve of theparent sample under 1.2 GPa, we believe that its particularbehavior arises from the difference in the character between theﬁrst-order and second-order transitions under 0.8 GPa and
1.2 GPa, respectively.
Here, we comment some similarities and differences in the PS
state between the La5/8  xPrxCa3/8MnO3 (x¼0.4) (LPCMO) andpresent Eu0.6Sr0.4MnO3 (ESMO). In the previous works [9,10], itis believed that after zero-ﬁeld cooling procedure the manganite
system showing steplike magnetic transition stays in a lowtemperature phase separated state with a small, and almost time
independent fraction of FM regions dispersed within a CO matrix.
In other words, the low temperature PS state of the LPCMO
system is taken as a blocked one preventing a growth of FM
phase over the CO one in a ﬁnite time scale. On the other hand,
upon increasing temperature, the intermediate-temperature PS
state above 20 K accompanies the time evolution of the FM phase,resulting in an increased magnetization (unblocked PS state). We

T. Inomata et al. / Journal of Magnetism and Magnetic Materials 324 (2012) 3863–3869

1x10-412-2x10-4(224)-1x10-4

4T(204)

Intensity (arb. units)

4.2K
8K
20K

0

dL(H)/L(0)

3867

0T

-3x10-420

30

40-4x10-450
60
2θ (deg.)

70

80

4

-5x10-4

1x10-43

4

Gd doped sample

0T

4T
2T

decrease

2
H (T)

1

increase

0

Intensity (arb. units)-6x10-4

3

0T

58.8

59

2

-1x10-4

59.2
2θ (deg.)

59.4

59.6

-2x10-4
Intensity (arb. units)-4x10-4-5x10-4

0

1

2

3
H (T)

4

5

0T
4T
2T

6

Fig. 4. (a) Isothermal magnetostriction dLðHÞ=Lð0Þ of Eu0.6Sr0.4MnO3 under ambient pressure at selected temperatures of 4 K, 8 K, and 20 K after zero ﬁeld cooling.
The arrows labeled 1 and 4 denote dLðHÞ=Lð0Þ at 4.2 K, before and after the stepliketransition. The arrows 2 and 3 represent the net and apparent variations indLðHÞ=Lð0Þ at 4.2 K. (b) Isothermal magnetostriction of (Eu0.9Gd0.1)0.6Sr0.4MnO3under ambient pressure at 4.6 K.

notice that a similarity in the temperature-magnetic ﬁeld phase
diagram including the MT curve between polycrystalline LPCMO
and ESMO. In fact, the magnitude of ZFC magnetization under 1 T
in Fig. 1 is strongly suppressed at low temperatures below 20 K,
which is due to the existence of a blocked phase separated regime
in that temperature range. In this regime, the energy barriers
separate the FM and non-FM states, leading to the coexistence
between the FM and non-FM phases. The application of externalpressure lowers the barriers between the FM and non-FM phases.
In the ZFC curve measured at 0.8 GPa, the low temperature PS
state is limited at lower temperatures below 10 K in comparison
to the magnetization data without pressure. However, it should
be noted that the PS state of the present samples is composed of
the FM clusters embedded within paramagnetic matrix since thetemperature dependence of the magnetization exhibits such noclear CO and/or AFM transition above Curie temperature as
LPCMO. In LPCMO system, upon decreasing temperature the COphase is stable in a long range manner below T co  230 K, then the
FM phase starts to order near T c  80 K and ﬁnally the PS state is

0T

69

69.2

69.4
69.6
2θ (deg.)

69.8

decrease-3x10-4

increasedL(H)/L(0)070Fig. 5. (a) X-ray powder diffraction proﬁles of a powder Eu0.6Sr0.4MnO3 inmagnetic ﬁelds at 10 K after zero ﬁeld cooling. The arrows point to the two peaks
corresponding to the Miller indices (204) and (224), respectively. (b) Field
dependence of the X-ray reﬂection peak located near 2y ¼ 601 recorded at 10 K
upon increasing H up to 4 T and then decreasing it down to zero. (c) Field
dependence of the peak around 2y ¼ 701.

formed below 20 K through the FM and CO states. In the PS stateof the LPCMO system, the CO matrix coexists with FM clusters,
while for the EuSrMnO system the FM and CO clusters are
dispersed within the PM matrix [15]. This type of PS state with
the PM matrix is also common to the (La0.4Pr0.6)1.2Sr1.8Mn2O7
bilayered manganite, where a ﬁeld-induced steplike transition
appears at low temperatures [8].
Next, we estimate a tolerance factor, t, using the averaged
ionic radius of A site cations ðr A ¼ ð1xÞr RE þ xr AE Þ, which is related
to the effective one-electron bandwidth of the manganite sample[21]. In addition to it, we evaluate the variance of the ionic radii,Ps2 ¼ ðxi r 2i r2A Þ, where xi and ri are the fractional occupancies
and the effective ion radii of cations of RE3 þ and AE2 þ , respectively [22]. For the parent sample, we obtain t ¼0.9183 and2
s2 ¼ 8:66  103 Å . For
the Gd substituted sample, t ¼0.9180
22
and s ¼ 8:79  103 Å . The light Gd substitution for Eu gives
rise to a signiﬁcant change in s2 between the parent and Gd 10%

3868

T. Inomata et al. / Journal of Magnetism and Magnetic Materials 324 (2012) 3863–3869

accompanies the ultrasharp lattice deformation at the same
critical ﬁeld.
Finally, we give some comments on the effect of pressure on themagnetostriction in a bilayered manganite because it seems to becontrary to that found in the present work [23]. Following theneutron diffraction study of the LPMSO bilayered manganite crystal
under hydrostatic pressure [24], the applied pressure lowers thecritical ﬁeld of the ﬁeld-induced FM states but broads the PM to FM
transition region. The external pressure strengthens the DE interaction in the bilayers, while it weakens the super exchange interaction
between the adjacent bilayers. This ﬁnding is close to a different
response of crystal structure to the applied pressure between
bilayered and cubic manganites. In addition, we note that in theprevious works on the effect of pressure on the transport, magnetization, and magnetostriction of Eu0.58Sr0.42MnO3 compound by several
authors, novel phenomena such as steplike magnetic transition and/or its associated magnetostriction are never referred [20,25,26].

1x10-4
1.2GPa0dL (H)/L(0)-1x10-40GPa
0.8GPa-2x10-4-3x10-4-4x10-4-5x10-4-6x10-4

0

1

2
H (T)

3

4

5. Summary

2x10-4
1.2GPa6

1x10-4-1x10-4

5.5

0 GPa
0.8 GPa-2x10-4
5-3x10-4

Bath temperature (K)dL (H)/L(0)0-4x10-44.5-5x10-4-6x10-4

0

1

2
H (T)

3

4

We have investigated the inﬂuence of external pressure on the
steplike magnetic transition and its concomitant magnetostriction in the polycrystalline (Eu,Gd)0.6Sr0.4MnO3. A suppression of
the energy barrier separating between the FM and non-FM states
under pressure leads to lowering the critical ﬁeld. The further
application of external pressure up to 1.2 GPa on the parent
sample substantially weakens the low temperature phase separated state, resulting in collapses of the ultrasharp metamagnetictransition and its concomitant lattice striction. X-ray diffraction
patterns of the parent sample taken under high ﬁelds at low
temperatures show the stable decrease of average lattice parameters, which is consistent with the magnetostriction behavior.
Our data indicate the importance of the low-temperature phasesegregated state in the doped manganite system exhibiting the
steplike transition.

Fig. 6. Isothermal magnetostriction dLðHÞ=Lð0Þ of the parent sample as a functionof the applied pressure at selected temperatures of both (a) 20 K and (b) 4.2 K. In(b), the bath temperature is monitored as a function of the external magnetic ﬁeld
under ambient and hydrostatic pressures. We note that the apparent change indLðHÞ=Lð0Þ is removed.

Acknowledgments

samples and results in an increase of the magnitude of disorder,
keeping the band width almost constant. For the Gd doped
sample, the local lattice distortion induced by the Gd substitution
produces the stronger phase separated state, which corresponds
for the higher critical ﬁeld attaining the ﬁeld induced FM transition. We expect that the application of the external pressure on
the Gd doped sample relaxes the lattice distortion around the Gd
ion and weakens the effect of quenched disorder.
The application of external pressure on the magnetostriction of
the sample studied lowers the critical ﬁeld, but the steplike
behavior in dLðHÞ=L at 4.2 K is not changed under a high pressureof 0.8 GPa, as well as the effect of pressure on the magnetization,
as shown in Fig. 4. Both the magnetization and magnetostriction
data point to the steplike volume shrinkage associated with theferromagnetic magnetic transition, which does not agree with theprevious measurement on polycrystalline Sm1  xSrxMnO3 [7]. We
suppose that a strain gauge attached with the sample will be notresponsible for a rapid variation although the reason is not madeclear. It is interesting to note that a steplike lattice transformationof single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 (LPSMO) bilayered
manganite is established by the application of magnetic ﬁeld.
Accordingly, it is reasonable that the steplike magnetic transition

References

This work was partially supported by a Grant-in-Aid for
Scientiﬁc Research from Japan Society of the Promotion of
Science.

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