Biomedical Engineering Reference
In-Depth Information
15
Characterization of Magnetic Nanoparticles Using Magnetic
Force Microscopy
Gunjan Agarwal
15.1
Introduction
The aim of this chapter is to provide an overview of the magnetic force microscopy
(MFM) technique and its application for the characterization of magnetic nano-
particles (MNPs). The chapter also serves as a user's guide to MFM, without
unnecessary repetition of previously published information, and without excessive
mathematical detail. The reader is introduced to physical principals of MFM, the
properties of MFM probes, probe calibration, methods of MFM detection, and
application of MFM for MNPs. The goal is not to provide a detailed overview of
MFM and hardware design, as several excellent texts (cited in the references) are
available for this purpose. Rather, the special considerations and challenges
required for MFM studies of MNPs, especially in biological samples, are high-
lighted. The chapter concludes with some details of the recent developments and
future trends in MFM of MNPs for the life sciences.
15.2
Development of MFM
Understanding the nature of magnetism at the nanometer-length scale is of inter-
est from a fundamental perspective, as well as for the development of next genera-
tion of MNPs for the life sciences. The study of MNPs involves special challenges
since, below a critical dimension, the competition between magnetostatic energy
and exchange energy is predicted to suppress magnetic domain formation, leading
to single-domain structures. These single-domain MNPs not only possess low
magnetization values, as compared to bulk material, but may also have lower
coercivity or a superparamagnetic character at temperatures conducive to living
systems. Thus, specialized techniques are needed to understand and characterize
the magnetic nature of MNPs.
