Magnetic-field-dependent optical studies of a layered antiferromagnet Pr_1/2Sr_1/2MnO₃

Magnetic-field (H)-dependent optical conductivity spectra σ(ω) and dielectric constant spectra ε(ω) of a layered antiferromagnet (A-type) Pr_1/2Sr_1/2MnO₃ were presented. At 0.0 T in 4.2 K, the σ(ω) showed a small Drude-like peak in the far-infrared region and a broad absorption peak in the mid-infrared region. As H increased, large spectral weights were transferred from high- to low-energy regions with increase of the Drude-like peak. We found that a polaron picture could explain most of the H-dependent spectral changes. By analyzing the H-dependent spectral weight changes and ε(ω), we showed that a dimensional crossover from a two-dimensional to a three-dimensional metal could occur in Pr_1/2Sr_1/2MnO₃.