Experimental and theoretical studies of nanoparticles of antiferromagnetic materials

Steen Mørup, Daniel Esmarch Madsen, Cathrine Frandsen, Christian Robert Haffenden Bahl, Mikkel Fougt Hansen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The magnetic properties of nanoparticles of antiferromagnetic materials are reviewed. The magnetic structure is often similar to the bulk structure, but there are several examples of size-dependent magnetic structures. Owing to the small magnetic moments of antiferromagnetic nanoparticles, the commonly used analysis of magnetization curves above the superparamagnetic blocking temperature may give erroneous results, because the distribution in magnetic moments and the magnetic anisotropy are not taken into account. We discuss how the magnetic dynamics can be studied by use of magnetization measurements, Mössbauer spectroscopy and neutron scattering. Below the blocking temperature, the magnetic dynamics in nanoparticles is dominated by thermal excitations of the uniform mode. In antiferromagnetic nanoparticles, the frequency of this mode is much higher than in ferromagnetic and ferrimagnetic nanoparticles, but it depends crucially on the size of the uncompensated moment. Excitation of the uniform mode results in a so-called thermoinduced moment, because the two sublattices are not strictly antiparallel when this mode is excited. The magnetic dipole interaction between antiferromagnetic nanoparticles is usually negligible, and therefore such particles present a unique possibility to study exchange interactions between magnetic particles. The interactions can have a significant influence on both the magnetic dynamics and the magnetic structure. Nanoparticles can be attached with a common crystallographic orientation such that both the crystallographic and the magnetic order continue across the interfaces.
Original languageEnglish
JournalJournal of Physics: Condensed Matter
Volume19
Issue number21
Pages (from-to)213202
ISSN0953-8984
DOIs
Publication statusPublished - 2007

Fingerprint Dive into the research topics of 'Experimental and theoretical studies of nanoparticles of antiferromagnetic materials'. Together they form a unique fingerprint.

Cite this