Note on the Effect of Pressure on the Curie Point of Iron-Nickel Alloys

By applying Clapeyron's equation, an estimate is made of the increase of the Curie point of nickel with pressure, which comes out of the order of magnitude of 5×{}10^-5 degree per atmosphere. For iron-nickel alloys, the increase of Curie point with pressure would become less as more iron is added, becoming zero with something like 70 percent of nickel, and for the alloys containing more iron the Curie point would decrease with pressure. These magnitudes are such that it seems most unlikely that pressures existing in the iron-nickel core of the earth would raise the Curie point of the material enough so that it could be ferromagnetic at the temperatures existing inside the earth. This makes any ferromagnetic explanation of the magnetism of the earth most implausible.