Composition dependent room temperature structure, electric and magnetic properties in magnetoelectric Pb(Fe1/2Nb1/2)O-3-Pb(Fe2/3W1/3)O-3 solid-solutions

摘要

We report on the studies of room temperature (RT) crystal structure, electric and magnetic properties of (1-x) Pb(Fe1/2Nb1/2)O-3 - x Pb(Fe2/3W1/3)O-3 (PFN1-x - PFWx) (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) solid solutions through the measurements of X-ray diffraction, FTIR, scanning electron microscopy (SEM), Neutron diffraction, Raman, Magnetic, Mossbauer and ferroelectric measurements. FTIR spectra showed two main perovskite related transmission bands. The SEM analysis shows an average grain size of 2 mm for all the solid solutions. Rietveld refinement was performed on RT X-ray diffraction (XRD) and neutron diffraction (ND), which reveals, the monoclinic phase for x = 0.0 with space group Cm and Cubic phase for x = 1.0 with space group Pm-3m. In other words, increasing x, the samples exhibit a gradual phase transition from monoclinic to cubic. In addition, the Raman spectroscopy corroborates the change in structural symmetry from monoclinic (Cm) to cubic (Pm-3m) on varying x. The coexistence of both monoclinic and cubic symmetries was observed between x = 0.2-0.8. Magnetic measurements shows that, the magnetic phase transition from paramagnetic to antiferromagnetic (AFM) was observed at or above RT for x = 0.6 and above. The magnetic structure was refined using the propagation vector k = (1/2, 1/2, 1/2) and structure was found to be G-type antiferromagnetic. Magnetic properties (M-H loops) shows, a weak ferromagnetic behaviour with antiferromagnetic ordering at RT. At RT, x = 0.0-0.6 the samples exhibits disordered paramagnetic property but weakly coupled with antiferromagnetic domains. But, x = 0.8 and 1.0 samples show antiferromagnetic and they are weakly coupled with paramagnetic domains. The temperature dependent magnetization (M(T)) confirms, the augmentation of Neel temperature (T-N) from 155 K to 350 K on increasing x. Mossbauer spectroscopy confirms superparamagnetic nature with the presence of Fe in 3+ state and on increasing x, the spectra changes from doublet to sextet. The ferroelectric (P-E) study confirms the existence of ferroelectric ordering with leaky behaviour. The reasonable ferroelectric loops with antiferromagnetic properties indicate samples with x = 0.2-0.6 show good magnetoelectric characteristics and may find applications in multiferroics. (C) 2016 Elsevier B.V. All rights reserved.