Introduction to Nanotechnology

7.1. BASICS OF FERROMAGNETISM
7
NANOSTRUCTU RED
FERROMAGNETISM
In this chapter we discuss the effect of nanostructure on the properties of ferro-
magnets, and how the size of nanograins that make up bulk magnet materials affects
ferromagnetic properties. We will examine how control of nanoparticle size can be
used to design magnetic materials for various applications. In order to understand
the role of nanostructure on ferromagnetism, we will present a brief overview of the
properties of ferromagnets. In Chapter 4 we saw that certain atoms whose energy
levels are not totally filled have a net magnetic moment, and in effect behave like
small bar magnets. The value of the magnetic moment of a body is a measure of the
strength of the magnetism that is present. Atoms in the various transition series of
the periodic table have unfilled inner energy levels in which the spins of the electrons
are unpaired, giving the atom a net magnetic moment. The iron atom has 26
electrons circulating about the nucleus. Eighteen of these electrons are in filled
energy levels that constitute the argon atom inner core of the electron configuration.
The d level of the N = 3 orbit contains only 6 of the possible 10 electrons that would
Introduction to Nanotechnology, by Charles P. Poole Jr. and Frank J. Owens.
ISBN 0-471-07935-9. Copyright 0 2003 John Wiley & Sons, Inc.
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