192
DOC.
4
KINETIC THEORY LECTURE NOTES
Thus,
when the
magnetization
changes by
dI,
the
energy
content
of the
system
increases
by
-HdI.
This
formula
is
also
applicable
when
H
is
the molecular
field.
In that
case
H
=
WI,
so
that
E
=
-WIdI
=
w
2
magn
W dI
Contribution
to
the
specific
heat
[p. 43]
Jump
at T
=
Tm
confirmed
experimentally.[86]
Proof
that
in
seemingly
not
unmagnetized ferromagnetic
substances
saturation
magnetization
is
really
present.[87]
Hysteresis
qualitatively explained.
Paramagnetism,
with Weiss's
Force Taken into Account
-Io -
F(a)
a
=
^
©
=
^(H+WI)
pRT
«T
V"
=
M
N
M
_
I0V
_I0M
N N
pN
If
only infinitely
small fields
are
admitted,
then
a
=
3
I/. If
this
is
inserted
into
the
0
second
equation,
one
obtains