Multiferroic behavior, enhanced magnetization and exchange bias effect of Zn substituted nanocrystalline LaFeO3 (La(1-x)ZnxFeO3, x=0.10, and 0.30)

Nanocrystalline Zn-substituted lanthanum orthoferrite La(1-x)ZnxFeO3 (x=0.1 and 0.3) (LZFO1 for x=0.1 and LZFO2 for x=0.3) was prepared by a chemical co-precipitation method. The as-prepared samples were annealed at 500 degrees C for 12 h. The formation of the pure crystallographic phase of LaFeO3 (LFO) and the substitution of Zn2+ in the doped samples were confirmed by X-ray diffractograms. Magnetization curves and hysteresis loops in the range of 300-2 K showed that magnetization of the doped samples was considerably enhanced compared to that of the pristine LFO. The maximum enhancement factor of similar to 2.5 for the saturation magnetization measured at room temperature was found in LZFO2. Interestingly, an exchange bias effect was observed in the nanoparticles LFO and LZFOs, which suggest the formation of antiferromagnetic-ferromagnetic (AFM-FM) core-shell structure of the AFM nanoparticles of LFO and LZFOs. The hysteretic behavior observed in the polarization-electric field curves recorded at room temperature indicates the onset of ferroelectric ordering of the samples. The dielectric constant measured in the presence and absence of a magnetic field confirmed that the samples are type-II multiferroics with positive magneto-coupling effect. (C) 2012 Elsevier B.V. All rights reserved.