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H Nakao, Y Sawata, M Mizumaki, [Y Yamasaki](https://orcid.org/0000-0002-8560-3462), H Kuwahara, T Saitoh

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[Phase-separated state in the bilayer manganite investigated by scanning-type resonant soft X-ray scattering](https://mdr.nims.go.jp/datasets/91a2e130-fc2b-485d-882d-e24c75ba0f44)

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JPCSJ30101159.pdfJournal of Physics:Conference Series      PAPER • OPEN ACCESSPhase-separated state in the bilayer manganiteinvestigated by scanning-type resonant soft X-rayscatteringTo cite this article: H Nakao et al 2025 J. Phys.: Conf. Ser. 3010 012159 View the article online for updates and enhancements.You may also likeSpin, orbital and topological order inmodels of strongly correlated electronsWojciech Brzezicki-Static properties of 2D spin-ice as asixteen-vertex modelLaura Foini, Demian Levis, Marco Tarziaet al.-Six–vertex model with domain wallboundary conditions in the Bethe–PeierlsapproximationL F Cugliandolo, G Gonnella and APelizzola-This content was downloaded from IP address 144.213.253.16 on 20/06/2025 at 01:15https://doi.org/10.1088/1742-6596/3010/1/012159https://iopscience.iop.org/article/10.1088/1361-648X/ab448dhttps://iopscience.iop.org/article/10.1088/1361-648X/ab448dhttps://iopscience.iop.org/article/10.1088/1742-5468/2013/02/P02026https://iopscience.iop.org/article/10.1088/1742-5468/2013/02/P02026https://iopscience.iop.org/article/10.1088/1742-5468/2015/06/P06008https://iopscience.iop.org/article/10.1088/1742-5468/2015/06/P06008https://iopscience.iop.org/article/10.1088/1742-5468/2015/06/P06008https://pagead2.googlesyndication.com/pcs/click?xai=AKAOjss9XoANsyp2AC6-B1vOev--wXBqzAaREKyczvZ5TdwhxtlwMfDYoHJY_wDUaI-xXZnPCtWqUdc8U7WzCq4PPj_CJyUg-U8QGPXt5-l64QjibkaQaCaxR51bsjFSpRoFOHAVq9KXzlOILYVXYSCiWqRql7PXZOqgSON9HKYihVqAczArqSccjy73zvqDXMdvlQHCiS7sfoYvCQMNuNdxjaV9c5_nxte4aQvX7CsJdh_ZxHmgXxHA3hC6vMIX513975tJHBg8M7kzBzcyqjuDawV7ScMGboy_3WknnOev5cXczyQuKpJ030AIJJJmFgzLcNVhG1JG1QzZt12q79CEFdlNKJZPmIEaA4lCTxPrqybZ5HBf&sig=Cg0ArKJSzLAakTmRdtDu&fbs_aeid=%5Bgw_fbsaeid%5D&adurl=https://www.electrochem.org/248/registration%3Futm_source%3DIOP%26utm_medium%3Dbanner%26utm_campaign%3DIOP_248_Early_Reg%26utm_id%3DIOP%2B248%2BEarly%2BRegistrationContent from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd15th International Conference on Synchrotron Radiation Instrumentation (SRI 2024)Journal of Physics: Conference Series 3010 (2025) 012159IOP Publishingdoi:10.1088/1742-6596/3010/1/0121591Phase-separated state in the bilayer manganiteinvestigated by scanning-type resonant soft X-rayscatteringH Nakao1, Y Sawata2, M Mizumaki3, Y Yamasaki4, H Kuwahara5,and T Saitoh21Photon Factory, Institute of Materials Structure Science,High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan2Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan3Faculty of Science, Kumamoto University, Kumamoto 860-8555, Japan4National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan5Department of Physics, Sophia University, Tokyo 169-8555, JapanE-mail: hironori.nakao@kek.jpAbstract. Phase separation between the CE-type charge-orbital ordered (CE) phaseand the A-type antiferromagnetic ordered (A-AF) phase has been investigated in thebilayer manganite, La2−2xSr1+2xMn2O7 (x = 0.51), by resonant soft X-ray scattering(RSXS) at the Mn L2,3 edge. The order parameters of CE and A-AF phases weremeasured at 1/4 1/4 0 and 0 0 1 reflections, respectively, and the phase separation wasobserved at the intermediate temperature region. Using a scanning-type RSXS withan X-ray focused by a Fresnel zone plate, the real-space images of domains for both thecompeting CE-phase and A-AF-phase were successfully observed. In the phase-separatedstate, we revealed that the domain of the CE phase forms a stripe pattern, and it seemsto originate from the inhomogeneity of the chemical composition on sample.1 IntroductionIn strongly correlated electron system, giant physical responses, such as the colossal magnetoresistance(CMR) effect [1] and the gigantic magnetoelectric effect [2], have been discovered and have attracted muchattention. The competition between electronically ordered phases is crucial for these giant responses, andthe phase separation has been reported near the boundary between the competing phases [3]. Therefore,observing the domain distributions of the competing phases is essential for understanding the origin ofgiant response.Resonant X-ray scattering (RXS) is a powerful tool for observing the spatial ordering of electronicdegrees of freedom (i.e., charge, spin, orbital, and multipoles) [4]. Moreover, in the soft X-ray region,the RXS signal at the L2,3 edge (2p → 3d transition) can directly probe the 3d electronic state, which isimportant in understanding the physical properties in 3d transition-metal compounds, and the strong RXSsignals were reported in various kinds of materials. Thanks to the strong intensity, real-space imaging ofthe spin texture could be realized by the coherent diffraction imaging technique even at Photon Factory[5, 6], which is an old synchrotron radiation facility.https://creativecommons.org/licenses/by/4.0/15th International Conference on Synchrotron Radiation Instrumentation (SRI 2024)Journal of Physics: Conference Series 3010 (2025) 012159IOP Publishingdoi:10.1088/1742-6596/3010/1/0121592Figure 1: (a) Schematic view of diffractometer for a scanning-type resonant soft X-ray scattering. AFresnel zone plate (FZP), order sorting aperture (OSA), sample, and silicon drift detector (SDD) areplaced. Photographs of (b) four-circle diffractometer, and (c) experimental configuration to observe thesignal at the 1/4 1/4 0 reflection.The hole-doped bilayer manganite, La2−2xSr1+2xMn2O7, is a well-known system exhibiting the CMReffect [1], and LaSr2Mn2O7 (x = 0.5) exhibits the phase separation between the CE-type charge-orbitalordered (CE) phase and the A-type antiferromagnetic ordered (A-AF) phase [7, 8]. Moreover, it wasreported that the order parameters of CE and A-AF phases can be observed by resonant soft X-rayscattering (RSXS) at 1/4 1/4 0 and 0 0 1 reflections, respectively [9]. Hence, it was selected as thefirst target to measure the spatial distribution of the domains. In this study, a scanning-type soft X-ray diffractometer has been developed by integrating a focusing optical system as shown in Fig. 1(a).Finally, we have succeeded in observing the domain distributions of both the competing CE-phase andA-AF-phase.2 ExperimentsA high-quality single crystal of La2−2xSr1+2xMn2O7 was grown using the floating-zone method. Here,x = 0.51 was selected to achieve half doping, Mn3.5+, due to the presence of oxygen vacancies. Thelattice constants are a = 0.387 nm and c = 2.003 nm with the space group I4/mmm. The crystal wascleaved parallel to the ab-plane, and (1 1 0) surface cut and polished with a fine emery paper to detectthe order parameters of the CE and A-AF phases. RSXS measurements were performed near the Mn L2,3edge at BL-16A [10] and BL-19B, Photon Factory, KEK. A π-polarized X-ray from the APPLE-II typeundulator was used. The [110]-[001] plane became the scattering plane as shown in the inset of Fig. 1(a).Hence, the 1/4 1/4 0 and 0 0 1 reflections are observable by the ω-rotation, although we are unable tomeasure the same region of the sample for both reflections [11].In order to measure a spatial distribution of the domains, we installed a focusing optics, four-circle 0  50  100  150  200(b)Temperature (K)1/4 1/4 0 (642.9eV)0 0 1 (640.0eV)020406080100 635  640  645  650  655  660(a)Intensity (arb. units)Energy (eV)La2−2xSr1+2xMn2O7 (x=0.51)1/4 1/4 0 (180K)0 0 1 (140K)Figure 2: (a) Energy dependence and (b) temperature dependence of the scattering intensity at the 1/41/4 0 reflection (CE-phase; green closed circles) and at the 0 0 1 reflection (A-AF-phase; orange opencircles).15th International Conference on Synchrotron Radiation Instrumentation (SRI 2024)Journal of Physics: Conference Series 3010 (2025) 012159IOP Publishingdoi:10.1088/1742-6596/3010/1/0121593(a) 1/4 1/4 0 200K−0.88 −0.86 −0.84 −0.820.300.320.340.360.380.40z (mm)(b) 210K−0.88 −0.86 −0.84 −0.82x (mm)0.300.320.340.360.38(c) 220K642.9 eV−0.88 −0.86 −0.84 −0.820.300.320.340.360.38Intensity (counts) 0 5000 10000 15000 20000 25000 30000Figure 3: Spatial distribution of the scattering intensity of the 1/4 1/4 0 reflection (a) at 200 K, (b)at 210 K, and (c) at 220 K. The figure roughly compensates for the shift in the z-direction due to thethermal expansion of the cryostat.diffractometer, and xyz-stages into our in-vacuum diffractometer [12]. Here, the piezo stages were usedto scan the sample position on a nanometer resolution as shown in Fig. 1(b). Unfortunately, the z-stagewas motor-driven due to weight limitation in this measurement, which limited the resolution to 500 nm.However, we plan to replace it with a high-load piezo stage in the near future. A small cryostat thatcan be placed on this small diffractometer was also developed, and the lowest temperature is 30 K. AFresnel zone plate (FZP) is utilized as the focusing optics, and the diameter is 320 μm with the centerstop diameter 100 μm. The focal length is f = 16.5 mm at 640 eV to maintain a large working distancearound the sample, even though the order sorting aperture (OSA) exists in the radiation shield of thecryostat as shown in Fig. 1(c). We selected the size of virtual light source upstream of FZP to efficientlydetect the signal by the silicon drift detector (SDD). However, the focused beam size depends on thevirtual source size. As a result, the focused beam size was about 3 μm when measuring the CE phase(Fig. 3), and it was about 300 nm when measuring the A-AF phase (Fig. 4). The beam size was estimatedby a wire-scan. However, it was difficult to put the sample exactly at the focal point. Hence, the spatialresolution of the intensity map is worse than the beam size.3 Results and discussionRXS signals were searched at the 1/4 1/4 0 and 0 0 1 reflections near the Mn L2,3 edge, and the energyspectra were measured as shown in Fig. 2(a). The spectra are consistent with the previous report [9],although there are differences in some details. The temperature dependence of the scattering intensityof the 1/4 1/4 0 reflection was observed at 642.9 eV with the cooling process as shown in Fig. 2(b). Thesignal appears below 215 K and it almost saturates around 180 K. Then, the intensity gradually reduceswith decreasing temperature, and almost vanishes at around 50 K. The temperature dependence of thescattering intensity of the 0 0 1 reflection was observed at 640.0 eV with the heating process. The signaldisappears at around 180 K (= TAN ). It indicates that the growth of the A-AF phase causes a collapse ofthe CE phase. Namely, the phase separated state between the CE phase and A-AF phase is expected toemerge in the temperature range of 50 K to 180 K.In the manganite system, it is noteworthy that the phase-separated state is expected to emergeelectronically without any inhomogeneity in the chemical composition on sample [13]. To detect suchthe electronic competition, we first noted the creation of the CE phase. The spatial distribution of thescattering intensity of the 1/4 1/4 0 reflection was measured at 642.9 eV as shown in Fig. 3. Domainsof several tens of micrometers in size could be observed clearly at 200 K. With increase temperature,the intensity become weak uniformly, though the domain position shifts in the z direction due to thethermal expansion of the cryostat. The signal completely disappears at 220 K in this intensity scale.Then the domain distribution was measured with the cooling process. However, we observed nearly thesame spatial distribution of domains, although a different domain pattern was expected for each thermalprocess.Next, the spatial distribution of the scattering intensity of the 0 0 1 reflection was measured at 640.0 eVas shown in Fig. 4. The signal was strong at the 0 0 1 reflection; therefore, a small pin-hole was used asthe virtual light source. Hence, the spatial resolution is better than that of Fig. 3. As the observationregion, the large domain of the A-AF phase was selected at 50 K. With increasing temperature, theintensity become weak, and the stripe pattern along the x-direction emerges as shown in Fig. 4(b). Inthe stripe region at z ∼ 0.03, 0.05, the intensity almost disappears, namely the A-AF phase is strongly15th International Conference on Synchrotron Radiation Instrumentation (SRI 2024)Journal of Physics: Conference Series 3010 (2025) 012159IOP Publishingdoi:10.1088/1742-6596/3010/1/0121594(a) 0 0 1 50K−1.52 −1.50 −1.480.080.100.12z (mm)(b) 140K−1.52 −1.50 −1.48x (mm)0.040.06(c) 220K640.0 eV−1.52 −1.50 −1.48−0.020.000.02Intensity (counts) 0 2000 4000 6000 8000 10000 12000Figure 4: Spatial distribution of the scattering intensity of the 0 0 1 reflection (a) at 50 K, (b) at 140 K,and (c) at 220 K. The figure roughly compensates for the shift in the z-direction due to the thermalexpansion of the cryostat.suppressed. In this temperature region, the phase separation between the CE phase and A-AF phaseoccurred. Hence, we can think that the A-AF phase changes into the CE phase in the stripe regionwith increasing temperature from 50 K to 140 K. On the other hand, the scattering intensity of the 0 01 reflection monotonically decreases towards TAN in the other region. The signal completely disappearsat 220 K as shown in Fig. 4(c). Then, with the cooling process, we observed nearly the same spatialdistribution of domains again including the stripe pattern. Therefore, these results reveal that the phase-separated pattern at this size scale is independent of the thermal process. A similar stripe structurewas reported in the bilayer manganite, and the stripe run perpendicular to the crystal-growth direction[14]. It was discussed to originate from the modulation of chemical compositions or lattice parametersfrozen in the process of crystal growth. In present case, the stripes also run perpendicular to the crystal-growth direction. Hence, the observed stripe pattern seems to originate from the inhomogeneity of thechemical composition on sample. To elucidate a purely electronic phase-separated state, it is importantto investigate within a stripe region, where the CE phase and A-AF phase compete with each other atthe intermediate temperatures.In conclusion, we have developed a scanning-type soft X-ray diffractometer to investigate the spatialdistributions of the domains. Utilizing the RSXS technique, the CE phase and the A-AF phase inLa2−2xSr1+2xMn2O7 (x = 0.51) could be observed at the 1/4 1/4 0 and 0 0 1 reflections, respectively.Moreover, we succeeded in observing the spatial distributions of the domains of the CE and A-AF phaseby the scanning-type RSXS. The domain of the CE phase forms the stripe pattern, and consistentlyappears in the same position on the sample. This may be caused by inhomogeneity in the chemicalcomposition of the sample. Further studies are desired to understand the phase-separated state as a keyof the giant responses.AcknowledgementsWe wish to thank Mechanical Engineering Center at KEK for their kind support in the developmentof the imaging measurement system. This work was supported by a Grant-in-Aid for TransformativeResearch Areas (A) ”Asymmetric Quantum Matters”, JSPS KAKENHI Grant Number JP23H04867, andby a Grant-in-Aid for Challenging Research (Pioneering) JSPS KAKENHI Grant Number JP22K18271.This study has been carried out under the approval of the Photon Factory Program Advisory Committee(Proposal Nos. 2019G553, 2021PF-S003 and 2024G041).References[1] Moritomo Y, Asamitsu A, Kuwahara H and Tokura Y 1996 Nature 380 141[2] Kimura T, Goto T, Shintani H, Ishizuka K, Arima T and Tokura Y 2003 Nature 426 55[3] Tokura Y 2006 Rep. Prog. Phys. 69 797[4] Matsumura Y, Nakao H and Murakami Y 2013 J. Phys. Soc. Jpn. 82 021007[5] Ukleev V, Yamasaki Y, Morikawa D, Kanazawa N, Okamura Y, Nakao H, Tokura Y and Arima T2018 Quantum Beam Sci. 2 315th International Conference on Synchrotron Radiation Instrumentation (SRI 2024)Journal of Physics: Conference Series 3010 (2025) 012159IOP Publishingdoi:10.1088/1742-6596/3010/1/0121595[6] Ukleev V, Yamasaki Y, Morikawa D, Karube K, Shibata K, Tokunaga Y, Okamura Y, Amemiya K,Valvidares M, Nakao H, Taguchi Y, Tokura Y and Arima T 2019 Phys. Rev. B 99 144408[7] Kubota M, Yoshizawa H, Moritomo Y, Fujioka H, Hirota K and Endoh Y 1999 J. Phys. Soc. Jpn.68 2202[8] Wilkins S B, Hatton P D, Prabhakaran D and Boothroyd A T 2003 Phys. Rev. Lett. 90 187201[9] Wilkins S B, Stojic N, Beale T A W, Binggeli N, Hatton P D, Bencok P, Stanescu S, Mitchell J F,Abbamonte P and Altarelli M 2006 J. Phys: Condens. Matter 18 L323[10] Amemiya K, Sakamaki M, Koide T, Ito K, Tsuchiya K, Harada K, Aoto T, Shioya T, Obina T,Yamamoto S and Kobayashi Y 2013 J. Phys.: Conf. Ser. 425 152015[11] In RSXS measurements, we can only observe the surface of the sample, because the penetrationdepth is quite shallow in the soft X-ray region.[12] Nakao H, Yamasaki Y, Okamoto J, Sudayama T, Takahashi Y, Kobayashi K, Kumai R and Mu-rakami Y 2014 J. Phys.: Conf. Ser. 502 012015[13] Moreo A, Yunoki S and Dagotto E 1999 Science 283 2034[14] Tokunaga Y, Tokunaga M and Tamegai T 2005 Phys Rev. B 71 012408