Size effects on the magnetic properties of LaCoO₃ nanoparticles

Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, P.R. China

^a e-mail: zhangtao@issp.ac.cn

Received: 15 July 2011
Revised: 7 December 2011
Accepted: 21 December 2011
Published online: 15 February 2012

Abstract

Magnetic properties of LaCoO₃ nanoparticles prepared by a sol-gel method with average particle size (D) ranging from 20 to 500 nm are investigated. All samples exhibit obvious ferromagnetic transition. With decreasing particle size from 500 to 120 nm, the transition temperature T_c decreases slightly from 85 K, however T_c decreases dramatically when D ≤ 85 nm. Low-field magnetic moment at 10 K decreases with reduction of particle size, while the high-field magnetization exhibits a converse behavior, which is different with previous reports. The coercivity H_c decreases as the particle size is reduced. It is different with other nanosystems that no exchange bias effect is observed in nanosized LaCoO₃ particles. These interesting results arise from the surface effect induced by sized effect and the structure change in LaCoO₃ nanoparticles.