Dimensional crossover driven by magnetic ordering in optical conductivity of Pr 1 / 2 Sr 1 / 2 MnO 3

We investigate optical properties of ${\mathrm{Pr}}_{1/2}{\mathrm{Sr}}_{1/2}{\mathrm{MnO}}_{3},$ which has A-type antiferromagnetic ordering at a low temperature. The temperature dependence of spectral weight transfer shows a clear correlation with the magnetic phase transition. Through the comparison with the results of ${\mathrm{Nd}}_{1/2}{\mathrm{Sr}}_{1/2}{\mathrm{MnO}}_{3},$ which has CE-type antiferromagnetic charge ordering, we showed that optical properties of ${\mathrm{Pr}}_{1/2}{\mathrm{Sr}}_{1/2}{\mathrm{MnO}}_{3}$ near the N\'eel temperature could be explained by a crossover from three-dimensional to two-dimensional metals. Details of the spectral weight changes are consistent with the polaron picture.