Thin film growth of multiferroic BiMn2O5 using pulsed laser ablation and its characterization

Abstract

Single phase polycrystalline thin films of multiferroic BiMn2O5 have been prepared on an LaAlO3 (LAO) substrate using the pulsed laser deposition technique. X-ray diffraction and Raman scattering data show that the films are highly strained and have a single phase orthorhombic structure. Near edge x-ray absorption fine structure data of the O K-edge and the Mn L-3,L-2-edge show no change in the electronic structure and the valence state of the BiMn2O5 thin films from that of the bulk. However, magnetic measurements performed over a wide range of temperature (2-300 K) and field (0-2 T) demonstrate a spectacular change in the magnetic behaviour of the BiMn2O5 thin films compared with the bulk. The zero field cooled magnetization confirms the antiferromagnetic transition, similar to the bulk sample, whereas field cooled magnetization data, surprisingly, show spin glass (SG) behaviour. The antiferromagnetic ordering at low temperature (5 K) is confirmed from M-H hysteresis measurements. Atomic force microscopy (AFM) measurement used to study the surface morphology shows unevenly spaced patterns of size similar to 1-2 mu m, separated by ridges of peak-to-valley height similar to 40 nm. The observed magnetic behaviour is explained in the context of the highly strained structure of the films as observed by XRD, Raman scattering and AFM data.