Magnetic dipole interactions in dysprosium ethyl sulphate II. Magnetic and thermal properties between 1 °K and the Curie point

The thermal and magnetic properties of dysprosium ethyl sulphate have been measured in the temperature range from 1 °K down to its Curie temperature of 0⋅13 ± 0⋅01 °K. Because of the extreme anisotropy of the spectroscopic splitting factor (gII = 10⋅8, g⊥ = 0) and the fact that magnetic dipole interaction between the ions predominates the system behaves like an Ising model. This fact allows the calculation of the magnetic and thermal properties of the system in a simple manner and good agreement is obtained with experiment. The particular properties of this salt also allow the measurement of its specific heat by each of the three methods (electrical heating, X-ray heating and relaxation heating) which may be employed at temperatures below 1 °K and excellent agreement is obtained.