Magnetic Thermometry

a method of temperature measurement that is used mainly below 1°K. The magnetic susceptibility x °f a paramagnet is the thermometric property used in the method. A paramagnet is chosen in which x is a very simple function of temperature: x = C/T. The magnetic temperature T^* is found from the value of x in a weak magnetic field when the value of C for the paramagnetic material is known. In the range of temperatures where Curie’s law is valid, T^* agrees with the thermodynamic temperature T. As the temperature is lowered, Curie’s law is no longer accurate, and T^* can differ appreciably from T. In practice the magnetic temperature is converted to the thermodynamic temperature by means of tables and curves compiled from careful investigations of the susceptibility x of paramagnetic salts as a function of temperature.