Optical detection of the rotation of orbital stripes in a charge–orbital ordered bilayer manganite at half-doping

Abstract

The CE magnetic order of charge–orbital ordering pattern in half-doped manganites is characterized by the formation of orbital stripe as well as the checkerboard-type charge ordering. The quasi-one-dimensionality in the orbital arrangement results in the in-plane anisotropy of physical properties, e.g., optical spectra with light polarization along the orbital stripe exhibits the larger energy-gap state than those along the orbital chain. It has been recently reported that the spontaneous rotation of orbital stripe with variation of temperature ( T ) occurs in a bilayer manganite, Pr ( Sr 0.1 Ca 0.9 ) 2 Mn 2 O 7 . To confirm this peculiar behavior, we performed optical measurements of a single domain sample with polarization dependence. While the in-plane optical anisotropy is identified together with the initial formation of the charge–orbital ordering, it is reversed at a lower T , where the orbital stripe is rotated by 90 ∘ .