Size effect on magnetic and dielectric properties in nanocrystalline LaFeO₃

Abstract

Nanocystalline LaFeO₃ powders with different grain sizes (30–150 nm) have been synthesized by a polymerized complex method to investigate their magnetic and dielectric properties. Thermogravimetric–differential thermal analysis curves of the precursory powders reveal the thermal decomposition and crystallization temperature should be at above 650 °C. The precursory powders were sintered at temperatures of 650, 700, 800, and 900 °C for 2 h. X-ray diffraction identify that all the samples are phase-pure. Weak ferromagnetic behaviors and finite exchange bias (EB) effects were observed for all the samples at room temperature, and both M_r and H_EB decreases monotonically with the increase of grain size. For 30 nm sample, the remnant magnetization and the EB field are 0.086 emu/g and 310 Oe, respectively. On the other hand, the dielectric constants decrease with the decreasing of grain size. Among all the samples, 150 nm samples show the largest dielectric constant about 6 × 10³.