Photon Factory Activity Report 2004 #22 Part B (2005)
Electronic Structure of Condensed Matter

1C, 2C/2002S2-002

In-situ angle-resolved photoemission study on La1-xSrxMnO3 thin films
1*211Akira CHIKAMATSU , Hiroki WADATI , Hiroshi KUMIGASHIRA , Masaharu OSHIMA ,2334Atsushi FUJIMORI ,Tsuyoshi OHNISHI , Mikk LIPPMAA , Kanta ONO ,Masashi KAWASAKI5, and Hideomi KOINUMA612Department of Applied Chemistry, The University of Tokyo, Tokyo 113-8656, Japan
Department of Complexity Science and Engineering, The University of Tokyo, Kashiwa 277-8561, Japan
3
Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
4
Institute of Materials Structure Science, KEK-PF, 1-1 Oho, Tsukuba 305-0801, Japan
5
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
6
Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan

Introduction
Hole-doped
perovskite
manganeseoxidesLa1-xSrxMnO3 (LSMO) have attracted much attention
because of their interesting magnetic and electronic
properties such as colossal magnetoresistance,
1
half-matallicity, and metal-insulator transition. In
order to clarify the origin of their physical properties,
it is necessary to obtain the information on the band
structures of these oxides and their changes as afunction of hole concentration (x). In this study, we
have performed in-situ angle-resolved photoemission(in-situ ARPES) study on well-ordered surfaces ofLSMO (x = 0.1, 0.2, 0.3, and 0.4) thin films grown
epitaxially on SrTiO3 (001) substrates by laser
molecular beam epitaxy (laser MBE).
Experimental
The LSMO thin films were fabricated in a laser
MBE chamber connected to a synchrotron radiation
photoemission system at BL-1C of the Photon
2Factrory. LSMO thin films were deposited on theTiO2-terminated SrTiO3 (001) substrates at 1050 ºC at-4
the oxygen pressure of 1 x 10 Torr. After cooling
down below 100 ºC, the films were transferred into
-10
the photoemission chamber under the vacuum of 10Torr. The PES spectra were taken with total energy
resolution of about 150 meV at the photon energy of88 eV.

Results and Discussion
Figure 1 shows the band structure of LSMO (a) x= 0.1, (b) x = 0.2, (c) x = 0.3, (d) x = 0.4 along theΓ−X direction determined by the in-situ ARPES
spectra (hν = 88 eV). As seen in Fig. 1(d), the band
structures of LSMO x = 0.4 consist of several highly
dispersive O 2p derived bands at the binding energies
of 2.3 – 6 eV, almost dispersionless Mn 3d bands at
2.0 eV, and an Mn 3deg derived electron pocket
centered at the Γ point. We find that the energy
positions of these bands monotonically shift towardhigher binding energy with decreasing holeconcentration in a rigid-band manner, whereas theelectron pocket which is clearly observed inferromagnetic metal LSMO x = 0.4 films graduallysmears out with decreasing x, and almost disappears
at ferromagnetic insulator LSMO x = 0.1 (Fig. 1(a)).
These results suggest that the pseudogap or gap
formation due to the spectral weight transfer from thenear-EF region dominates the changes in electronicstructure near EF of LSMO thin films with x.
References[1] M. Imada, A. Fujimori, and Y. Tokura, Rev. Mod.
Phys. 70 1039 (1998) and references therein.
[2] K. Horiba et al., Rev. Sci. Instrum, 74, 3406 (2003).
*chikamatsu@sr.t.u-tokyo.ac.jp

Figure 1: The band structure of LSMO (a) x = 0.1, (b) x = 0.2, (c) x = 0.3, (d) x = 0.4 along the Γ−X direction
determined by in-situ ARPES measurements (hν = 88 eV). Dark parts correspond to the energy bands.

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