Memory, Aging and Spin Glass Nature: A Study of NiO Nanoparticles

TL;DR

This study investigates the spin glass-like magnetic behavior of NiO nanoparticles, revealing aging and memory effects indicative of surface spin freezing, thus linking nanoparticle magnetism to spin glass phenomena.

Contribution

It provides experimental evidence of spin glass behavior in NiO nanoparticles and attributes this to surface spin freezing, a novel insight into nanoparticle magnetism.

Findings

NiO nanoparticles exhibit aging and memory effects.

Magnetic behavior resembles that of spin glasses.

Surface spin freezing causes the observed phenomena.

Abstract

We report studies on magnetization dynamics in NiO nanoparticles of average size 5 nm. Temperature and time dependence of dc magnetization, wait time dependence of magnetic relaxation (aging) and memory phenomena in the dc magnetization are studied with various temperature and field protocols. We observe that the system shows memory and aging in field cooled and zero field cooled magnetization measurements. These experiments show that the magnetic behavior of NiO nanoparticles is similar to spin glasses. We argue that the spin glass behavior originates from the freezing of spins at the surface of the individual particles.