7.7 Method of Adiabatic Demagnetization

A sketch of the apparatus used for adiabatic demagnetization is shown in Fig. 7.8. The substance S a paramagnetic salt of Gd2(SO4)8 H2O or FeNH4,(SO4)12 H2O is pressed into a sphere or ellipsoid. It is coated with a thin layer of stop-cock grease to prevent oxidation or dehydration. It is suspended by silk thread at the centre of the secondary coils which is used for measurement of susceptibility inside a calorimeter immersed in boiling helium at a temperature of about 1 K. This in turn is surrounded by a bath of liquid nitrogen. The whole system is placed between the pole pieces of electromagnet. To perform the experiment, the calorimeter is filled with helium at a pressure of 1 mm of Hg.



Fig. 7.8 ...

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