Composition-driven enhanced magnetic properties and magnetoelectric coupling in Gd substituted BiFeO3 nanoparticles

Abstract

Bi1-xGdxFeO3 (x=0, 0.05 and 0.1) samples were synthesized by modified sol–gel process. X-ray diffraction studies confirmed that the crystal structures of Gd substituted samples remain stable for x<0.1, while compositional-driven structural phase transition from rhombohedral to orthorhombic was observed in the case of x=0.1. The average particle sizes of pure and Gd substituted BiFeO3 nanoparticles were found to be in the range 62–46nm. The size of the oblate spherical particles decreased with increasing Gd concentration. XPS studies revealed the trivalent oxidation states of Bi and Fe ions along with sample purity. Pure BiFeO3 exhibited linear M–H loop indicating its antiferromagnetic characteristics, whereas obvious non-linear M–H loops were observed in Gd substituted samples. In contrast to the observed room temperature magnetization (0.36emu/g) under 40kOe for BiFeO3, the sample with 10% Gd exhibited appreciable enhancement of magnetization (1.88emu/g). A leaky type P–E hysteresis loop was observed for the pure one, whereas concave-like ferroelectric loops were obtained for Gd substituted samples. The possible origins of enhanced multiferroic properties have been explained on the basis of substituent, its concentration, phase purity, particle size, structural distortion and the modified magnetic structure. The measurement of magnetoelectric studies at room temperature revealed the coupling between magnetic and ferroelectric ordering, which is desirable for multifunctional device applications of multiferroics.