Thermodynamics, 5th Edition

(5.9.6b)

If the magnetization of the material in its normal state is essentially zero, and on setting ${\overline{ℳ}}_s=-{\mathscr{H}}_c/4\pi$, one obtains

$S_n-S_s=-(V/4\pi )[{\mathscr{H}}_c\cdot {(\partial {\mathscr{H}}_c/\partial T)}_P].$ (5.9.7)

(5.9.7)

Several points are to be noted. (i) First, the obvious analogy to the Clausius–Clapeyron equation. (ii) According to the third law, as T→0, the entropy of any material must reach a minimum value with zero slope; hence, ${(\partial {\mathscr{H}}_c/\partial T)}_P\to 0$ as well (cf. Figure 5.9.1). (iii) Experimentally ...