Environmental Engineering Reference
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of the moments take the form:
cos(
Q
·
R
i
+
ϕ
)
J
iη
=
J
⊥
sin(
Q
·
R
i
+
ϕ
)
J
iζ
=0
,
J
iξ
J
⊥
=
(1
.
5
.
1)
while the
longitudinal wave
, sometimes known in the heavy rare earths
as the
c-axis modulated structure
or CAM, is described by
J
iζ
=
J
cos(
Q
·
R
i
+
ϕ
)
,
(1
.
5
.
2)
with the two other components being zero. The wave-vectors
Q
are along
the
c
-axis, and the associated wavelength 2
π/Q
does not necessarily bear
any simple relationship to the lattice spacing.
Fig. 1.19.
Magnetic structures of the heavy rare earths. The moments
in a particular hexagonal layer are parallel, and the relative alignments
of different planes are illustrated. From left to right; the basal-plane
ferromagnet, the helix, the cone, and the longitudinal-wave structure.
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