Preparation of Gd doped La2SrMn2O7 layered manganites at inert atmosphere and investigation of their structural and magnetic properties

Abstract

Bulk polycrystalline samples of Gd doped La2-xGdxSrMn2O7 (x=0.3, 0.6) doubled-layered perovskite manganites were synthesized in air by conventional solid state reaction and then annealed at 6000C in inert (N2) atmosphere. Their structural, morphological and magnetic properties are investigated using different characterization techniques. X-ray diffraction technique was performed for the structural analysis and phase identification of the synthesized material. Powder X-ray diffraction patterns show impurity peaks for samples synthesized in air whereas annealing of the synthesized materials at inert atmosphere completely removes the undesired peaks in lightly (15%) Gd doped sample, partially removes impurities in heavily (30%) doped sample. Morphology of the samples obtained by FESEM analysis confirmed the formation of grains with micron scale and displayed that the grain size gradually decreases from 2µm to 0.8µm with the increase of Gd3+ doping. The morphology was improved in both samples due to annealing. The existence of all the desired elements in the prepared samples was ensured by Energy Dispersive X-ray spectroscopy (EDX) analysis. Magnetic properties of La2-xGdxSrMn2O7(x=0.3, 0.6) ceramics measured at room temperature. Magnetic hysteresis loops demonstrate enhanced magnetic softness for the lightly Gd doped manganite. Its saturation magnetization at room temperature at 10KOe is 50emu/gm and is increased 53emu/gm after heat treatment. Coercivity of this sample is 24Oe. Heat treatment at inert atmosphere has decreased coercivity 17Oe and also decreased remanent magnetization. The outcome of this investigation suggests that heat treated of 15% Gd doped La2SrMn2O7 enhances magnetic properties and soft ferromagnetic nature of the synthesized sample. The improved properties of this specific composition is associated with homogeneous reduced grain size and significant suppression of impurity phase. The enhanced magnetization along with small remanence and low coercivity indicate that 15% Gd doped La1.7Gd0.3SrMn2O7manganite may be used in applications where magnetic softness is desired.