Analysis of Debye-Waller—Factor and Mössbauer-Thermal-Shift Measurements. II. Thermal-Shift Data on Fe

Techniques developed in a previous paper are used to subtract the second-order Doppler contribution from measured thermal shifts on pure Fe and dilute Fe in various hosts. This allows the temperature dependence of the isomer shift arising from the electron density at the nucleus to be seen more clearly than was previously possible. It is shown that this temperature dependence cannot be accounted for by thermal expansion alone. In pure Fe a contribution related to the magnetization is clearly evident, as is theoretically expected. A contribution in addition to this and the thermal-expansion contribution is present, contrary to the conclusion generally drown from previous work. The additional contribution to the isomer shift is discussed in terms of two theories which have been used to explain the temperature dependence of hyperfine coupling constants.