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Charge/orbital/spin ordering in Mn-oxide thin films revealed by resonant soft x-ray scattering

Hole-doped perovskite manganese oxides R 1-x A x MnO 3 , where R is a rare-earth ( R = La, Nd, Pr) and A is an alkaline-earth atom ( A = Sr, Ba, Ca), have attracted great interest mainly due to the ordering of spin, charge, and orbitals. In thin films, such ordering is greatly affected by epitaxial-strain effects from substrates, and so far has been studied by hard x-ray diffraction [1]. In this study we investigated the spin/charge/orbital ordering in thin films of Pr 0.5 Ca 0.5 MnO 3 on LSAT (011) substrates (LSAT: (LaAlO 3 ) 0.3 -(SrAl 0.5 Ta 0.5 O 3 ) 0.7 ) by resonant soft x-ray scattering. The measurements were performed at 10ID-2 (REIXS) of the Canadian Light Source. Figure 1 shows the photon-energy dependence of the peak intensity of the (1/4, 1/4, 0) charge/orbirtal order reflection at 160 K. There is no polarization dependence at this temperature. Energy profiles change and polarization dependence appears below 150 K. This change corresponds to antiferromagnetic transition, which has also been observed in bulk samples ( T OO = T CO ~ 240 K > T N ~ 170 K). We also calculated the energy profiles by using configuration-interaction (CI) cluster-model calculations. By just considering the contributions from [Mn 3+ O 2- 6 ] octahedra, we obtained good agreement between experiment at 160 K and CI calculation.

[1] D. Okuyama et al ., Appl. Phys. Lett. 95 , 152502 (2009).