Low-temperature dynamics of magnetic nanoshells

¹ Department of Physics, Hong Kong University of Science and Technology - Clear Water Bay, Hong Kong, China
² Department of Chemistry, Hong Kong University of Science and Technology - Clear Water Bay, Hong Kong, China
³ Department of Chemistry, Brandeis University - 415 South Street, Waltham, MA 02454, USA
⁴ Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology - Thuwal 23955-6900, Kingdom of Saudi Arabia

^a xixiang.zhang@kaust.edu.sa

Received: 10 May 2010
Accepted: 26 August 2010

Abstract

Well and poorly crystallized iron oxide nanoshells (or hollow nanoparticles) were successfully fabricated using the Kirkendall effect in an oxygen and in an air environment using Fe nanoparticles. The low-field, zero-field–cooling (ZFC) and field-cooling (FC), measurements on these two samples indicated that the inter-particle interactions between the well-crystallized nanoshells were much stronger than those in the poorly crystallized nanoshell assembly. However, the memory experiments showed that there was no spin-glass phase in the well-crystallized nanoshell assembly, whereas the signature of the spin-glass phase (or the memory effect) was evident in the poorly crystallized nanoshell assembly. This result suggests that the origin of the spin-glass characteristic observed in the poorly crystallized nanoshells is the existence of the spin-glass phase within those particular nanoshells.