1895: Curie’s law - The book of science

Curie’s law
Magnetic thermometer
Magnetic susceptibility
Commentary

Curie’s law

The magnetization of a paramagnetic material
is directly proportional to the strength
of the exterior magnetic field and inversely
proportional to the temperature of the material.
What’s going on here? Pierre Curie discovered
this effect and explained that paramagnetic bodies
are like perfect gases . . . Ah . . .
What the heck are perfect gases?
I would have to guess—because it’s difficult
to pick a path through a forest of equations—
that magnetization results from particles in alignment
but heat jiggles the particles out of skew.

Magnetic thermometer

Curie’s law is the basis
of the magnetic thermometer
for measuring very low temperatures,
not to be confused with
a thermometer that has a magnetic mount.

Magnetic susceptibility

All materials are either intrinsically magnetic
or are susceptible to becoming diamagnetic or paramagnetic
under the influence of an external magnetic field.
Your magnetic susceptibility depends
on the sum of the spins of your unpaired electrons
or on the magnetic moments of your electron orbits.
If all materials were strongly diamagnetic
then your levitating vehicle could go anywhere.
For a major investment, we seek to make this a reality.
Your basic magnetic personality is totally
orthogonal; that is, that has nothing to do with it, or,
depending on your gullibility, is related to the percentage.

Pierre Curie built a sensitive torsion balance to measure the magnetization of paramagnetic bodies. The torsion balance was invented by John Michell and used by Henry Cavendish to measure the density of the earth, and by Charles-Augustin de Coulomb to derive the inverse-square law.

Pierre Curie also showed that above a certain transition point, known as the Currie temperature, a ferromagnet loses its intrinsic magnetization. Above that temperature, however, it still responds as a paramagnet to an external magnetic field.