Local probing of charge and orbital-ordering-induced anisotropy with polarization-modulated infrared reflection difference microspectroscopy

We investigated optical anisotropy of a Bi0.3 Ca0.7 MnO3+δ crystal induced by charge and orbital orderings using infrared reflection difference microspectroscopy in combination with polarization modulation. Besides a drastic change in the anisotropic response below the charge ordering transition around 16°C, we found an additional change in the optical anisotropy at a slightly lower temperature of around 13°C, which is accompanied by a rotation of the optical axis by 45°. We attribute this intriguing behavior to the signature of the orbital ordering that is not coincident with the charge ordering transition with decrease in temperature.