Adiabatic demagnetization of paramagnetic

Magnetic thermometry has been developed chiefly to measure temperatures near absolute zero (below -458°F, or -272°C). These measurements are obtained by adiabatic demagnetization of a paramagnetic salt. Inductance can be measured with an AC bridge (as shown in Figure 3.164) whose balance is independent of frequency. The relationship between self-inductance and sus-... 

Nuclear Adiabatic Demagnetization. Nuclear paramagnetism is based on the same principle as ordinary paramagnetism, but it allows achieving temperatures on the order of 10 K. This was first attained in 1956 by Kurti etal By demagnetizing copper from an initial magnetic field strength between 20,000 and 28,000 Oe and an initial temperature of 12 mK, a temperature of 20 juK was reached. Copper was used since internal thermal equilibrium is reached in minutes instead of hours. 

The paramagnetic salts useful for this type of thermometry are the same as that used in the ADR (adiabatic demagnetization refrigerator, see Section 7.3 and Fig. 7.7). The most commonly used salts are ... 

The technique of adiabatic demagnetization can be used to obtain temperatures below 1 K. This method, suggested by Peter Debye in 1926 and independently by William Giauque in 1927, requires a paramagnetic solid in which ions with unpaired electrons are sufficiently separated that at 1 K the orientations of the magnetic dipoles are almost completely random. Gadolinium(III) sulfate octahydrate, Gd2(804)3 8H2O, is commonly used. 

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