Controllable synthesis, XPS investigation and magnetic property of multiferroic BiMn2O5 system: The role of neodyme doping

In this work, a novel series of multiferroic materials BiMn2O5 doped by Neodyme has been prepared by a sol-gel method at low temperature. The crystallographic studies using X-ray diffraction and Rietveld Refinement techniques showed the formation of single-phase samples for all compositions, crystallizing in a mullite-type orthorhombic perovskite structure, space group Pbam (Z = 4). The SEM techniques confirmed the formation of single-phase materials with excellent mapping distribution. Raman and infrared spectroscopic measurements were performed and combined with lattice dynamics simulations to describe the room-temperature vibrational properties of all samples. The X-ray Photoelectron Spectroscopy (XPS) were measured in the energy range of 0-1400 eV at room temperature. The Fermi level E-F was defined with the accuracy of 0.127, 0.32 and 0.48 eV for BiMn2O5, Bi0.9Nd0.1Mn2O5 and Bi0.8Nd0.2Mn2O5 respectively. The X-ray photoelectron spectroscopy shows the existence of Mn4+ state. Magnetic measurements indicate Neel temperature T-N at 31, 40 and 61 K for BiMn2O5, Bi0.9Nd0.1Mn2O5 and Bi0.8Nd0.2Mn2O5 respectively.