Page 107 - Maxwell House

NEOCLASSICAL THEORY OF INTERACTION 87

Here ≅ / is called the electron gyromagnetic ratio and ≅ 2.21⋅ 10 [rad / (A∙ s/m)].
5

0
Note that the real spin movement is much more complicated and can be described correctly in
the framework of quantum mechanics. The expression (2.91) is only the first order
approximation.
Let consider the example. The samarium cobalt (SmCo), one of the strongest permanent
magnet, can create the bias magnetic field up to 3⋅ 10 A/m that shifts the resonance frequency
6
to = 2 = 2.21x10 ∗ 3x10 ⁄⁄ 5 6 2 = 105 GHz. Consequently, lowing the bias intensity
0
0
we can place the resonance frequency practically at any frequency of the microwave spectrum.
However, any free motion of particles in actual materials is impossible without never-ending
loss of their energy. Subsequently, the magnetic moment spirals in from its initial angle until it
is aligned with bias direction, as shown in Figure 2.7.1b. As soon as the procession has stopped,
all magnetic moments line up in the direction of the bias vector, and the ferrite reaches its

saturation magnetization = | | where N is the total number of aligned magnetic

moments per unit volume.
2.7.3 Force Precession in Fully Magnetized Ferrite

Now assume that the electromagnetic wave propagating in biased ferrite has RF H-field ()
in (2.90) of one of the special structure

() = () = cos ∓ sin (2.92)

0
±
0

Figure 2.7.2 demonstrates how the vector () changes in a rotary manner for the observer
±
looking from the bottom along the positive direction of the bias H-field. It is clear that the vector
() is polarized left-handed (see definition in Chapter 5) relative to the bias vector
+ 0 0
while the vector () moves in opposite direction. Both vectors make full turn for time =
−
2 = 1/ meaning the vector angular rotation and field frequency are always equal. As
⁄
soon as = , the tip of these vectors traces the perfect circles around the bias vector. Later

in Chapter 5 we will call such fields Circle Polarized (CP).
We chose H-field structure deliberately. Indeed, comparing Figure 2.7.2 with Figure 2.7.1b, we

Figure 2.7.2 Vector H-field over time: a) (), b) ()
−
+
can see that the vector () rotates exactly in the same direction as the free processing vector.
+
If so, the strong interaction between them is expected while similar interaction with () is
−
hindered due to mismatch in their direction of rotation.