Optical evidence of a pseudogap in the ferromagnetic metallic phase of the bilayered manganite

Low-energy (0.5 - 4 meV) charge dynamics have been investigated for a-axis-oriented thin films of the bilayered perovskite-type manganite La2-2xSr1+2xMn2O7 (x = 0.3) byusing THz time-domain spectroscopy. In the ferromagnetic metallic phase, we observed a clear gap signature, while the film exhibits paramagnetic insulator to ferromagnetic metal transition at 250 K according to the resistivity and magnetization measurements. This provides the evidence of a pseudogap in the ferromagnetic phase of La2-2xSr1+2xMn2O7 (x = 0.3). (C) 2004 Elsevier B.V. All rights reserved.