Chapter 11
Spintronics
11.1 Introduction
The materials that have been considered thus far in the book are ’classical,’ in the
sense that their electromagnetic properties are easily stated as parameters that can
be easily measured in the laboratory, or can be computed and understood using
’classical’ physics. This is true whether the materials are ’structural’ or ’biological’.
Furthermore, we have shown that materials of these two classes can be characterized
using the same classical electromagnetic models.
In order to expand our understanding and application of electromagnetic models
to materials, we must consider cases in which the above statements do not hold, and
one must resort to more sophisticated physical models that incorporate quantum
mechanical principles just to understand the interaction of the electromagnetic field
with the material. There are a number of common and novel materials in which this
is true. For example, the interaction of an electromagnetic field in a microwave solidstate maser can only be understood through the application of the quantum theory of
paramagnetism and electron spin dynamics [117]. Another well-known example is
nuclear magnetic resonance (NMR), in which the spin of the proton in the nucleus
of atoms provides the interaction that leads to magnetic resonance imaging (MRI).
11.2 Paramagnetic Spin Dynamics and the Spin Hamiltonian
In order to fully understand the possibilities of using paramagnetic phenomena to
detect lesions noninvasively, we must review a bit of electron-spin physics. Our
interest is in the dynamic response of spins to time-varying fields. These fields are
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
H. A. Sabbagh et al., Advanced Electromagnetic Models for Materials
Characterization and Nondestructive Evaluation, Scientific Computation,
https://doi.org/10.1007/978-3-030-67956-9_11
283
Spintronics
11.1 Introduction
The materials that have been considered thus far in the book are ’classical,’ in the
sense that their electromagnetic properties are easily stated as parameters that can
be easily measured in the laboratory, or can be computed and understood using
’classical’ physics. This is true whether the materials are ’structural’ or ’biological’.
Furthermore, we have shown that materials of these two classes can be characterized
using the same classical electromagnetic models.
In order to expand our understanding and application of electromagnetic models
to materials, we must consider cases in which the above statements do not hold, and
one must resort to more sophisticated physical models that incorporate quantum
mechanical principles just to understand the interaction of the electromagnetic field
with the material. There are a number of common and novel materials in which this
is true. For example, the interaction of an electromagnetic field in a microwave solidstate maser can only be understood through the application of the quantum theory of
paramagnetism and electron spin dynamics [117]. Another well-known example is
nuclear magnetic resonance (NMR), in which the spin of the proton in the nucleus
of atoms provides the interaction that leads to magnetic resonance imaging (MRI).
11.2 Paramagnetic Spin Dynamics and the Spin Hamiltonian
In order to fully understand the possibilities of using paramagnetic phenomena to
detect lesions noninvasively, we must review a bit of electron-spin physics. Our
interest is in the dynamic response of spins to time-varying fields. These fields are
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
H. A. Sabbagh et al., Advanced Electromagnetic Models for Materials
Characterization and Nondestructive Evaluation, Scientific Computation,
https://doi.org/10.1007/978-3-030-67956-9_11
283