When I worked at Dupont Pioneering Research Analytical in 1964 I developed the Curie point method for calibrating the Dupont
950 thermogravimetric analyzer (TGA)
TGA is a method for analyzing the thermal decomposition of materials especially organic polymers. A small sample of material
is placed in a platinum "boat" which is suspended from a tiny quartz rod. The quartz rod is one arm of a balance. A thermocouple
temperature measuring device is aligned next to the sample. A quartz tube is slid over the sample with a furnace around it.
The sample is heated to decomposition and the weight loss and temperature are recorded. There is an inherent problem in accurately
determining the transition temperatures because the thermocouple cannot touch the sample.
I solved the problem by putting a metal or other material of known Curie point (the temperature at which a material changes
from ferromagnetic to paramagnetic) in the sample "boat". The furnace was placed in a magnetic field. The effect of the magnetic
field made the material appear lighter. When the Curie point was reached the sample appeared to gain weight, thus providing
a calibration for the TGA. This technique has become the world wide laboratory standard. The calibrations are normally done
with Ni and Fe as well as alloys. I also tested CrO2 because Dupont was developing the material for recording tape in 1964.
CrO2 has a curie point of 122deg C. A subsequent Curie point method which is the subject of a patent filed in 1967
doesn't mention this material.