Artificial Construction of the Layered Ruddlesden-Popper Manganite La_2Sr_2Mn_3O_(10) by Reflection High Energy Electron Diffraction Monitored Pulsed Laser Deposition

摘要

Pulsed laser deposition has been used to artificially construct the n = 3 Ruddlesden-Popper structure La_2Sr_2Mn_3O_(10) in epitaxial thin film form by sequentially layering La_(1-x)Sr_xMnO_3 and SrO unit cells aided by in situ reflection high energy electron diffraction monitoring. The interval deposition technique was used to promote two-dimensional SrO growth. X-ray diffraction and cross-sectional transmission electron microscopy indicated that the trilayer structure had been formed. A site ordering was found to differ from that expected thermodynamically, with the smaller Sr~(2+) predominantly on the R site due to kinetic trapping of the deposited cation sequence. A dependence of the out-of-plane lattice parameter on growth pressure was interpreted as changing the oxygen content of the films. Magnetic and transport measurements on fully oxygenated films indicated a frustrated magnetic ground state characterized as a spin glass-like magnetic phase with the glass temperature X_g≈34 K. The magnetic frustration has a clear in-plane (ab) magnetic anisotropy, which is maintained up to temperatures of 150 K. Density functional theory calculations suggest competing antiferromagnetic and ferromagnetic long-range orders, which are proposed as the origin of the low-temperature glassy state.