Abstract
The pressure dependence of the hyperfine field ( nu ) of 27Al in iron has been measured under hydrostatic pressure at room temperature: ( delta ln nu / delta P)T was found to have the value -(6.26+or-0.10)*10-7 kg-1 cm2. Using this value it is shown that, while the normalised hyperfine field of 27Al decreased more slowly with temperature than that of 57Fe at constant pressure, it decreased more rapidly at constant volume. The functional form of the temperature dependence at constant volume is in agreement with spin wave theory.