Eur. Phys. J. B 78, 65-73 (2010)
https://doi.org/10.1140/epjb/e2010-00293-0

Memory and aging effects in antiferromagnetic nanoparticles

Department of Physics, Indian Institute of Technology Kanpur (U.P.), 208016 Kanpur, India

Corresponding author: ^a sunilkm@iitk.ac.in

Received: 25 May 2010
Revised: 12 August 2010
Published online: 6 October 2010

Abstract

We investigate slow dynamics of collection of a few noninteracting antiferromagnetic NiO nanoparticles. Our purpose is to enquire the role of size-dependent magnetization fluctuations in temperature and time dependent properties of antiferromagnetic nanoparticles. The zero-field cooled magnetization exhibits size dependent fluctuations. We find memory effects in field cooled magnetization, as well as aging effects in thermoremenant magnetization of antiferromagnetic nanoparticles. The antiferromagnetic nanoparticles show a stronger memory effect than the corresponding effect in the ferromagnetic particles, when the distribution of particles include very small sizes. The situation reverses for bigger sizes. The relaxation of the magnetization after a sudden cooling, heating and removal of fields reiterate the memory effects. We also see a weak signature of size-dependent magnetization fluctuations in aging effect of antiferromagnetic nanoparticles. We find a two-step relaxation of thermoremenant magnetization in antiferromagnetic case, which differs qualitatively from relaxation of ferromagnetic nanoparticles.