High-Field Studies of Band Ferromagnetism in Fe and Ni by Mössbauer and Magnetic Moment Measurements

High-field susceptibility XHF in Fe and Ni (at 4.2, 77, and 300 K) and high-field Mossbauer studies in Fe at 4.2°K are reported and related to the band structure of Fe and Ni and to band models of ferromag­ netism. The Mossbauer effect was employed to measure the change in the hyperfine field H n at the 57Fe nucleus with application of an external field. Assuming H n to be proportional to the bulk magnetization, a microscopic equivalent to XHF is obtained. We also show how the high-field data may be used alternatively to determine the nuclear g factor. The macroscopic differential magnetic moment measurements are pre­ sented along with an extensive discussion of the experiments to 150 kG. We find XHF =4.3X 10-5 emu/cc for Fe and 1.7X10-5 emu/cc for Ni at 4.2°K, where XHF is averaged from 50-150 kG. The interpretation of these low-temperature data (when reasonable estimates of Van Vleck susceptibility are made) indicates holes in both spin bands of Fe and a full band of one spin in N, in agreement with the accepted band theory picture for these metals and with recent spin-polarized and pseudopotential band calculations for magnetic Fe and Ni. The differential magnetic moment measurements at higher temperatures are in reasonable agreement with predictions of spin-wave theory. In the Appendices we include: (a) a tabulation of the field­ dependent terms which enter into the spin-wave description of the magnetization and their derivatives with respect to field and temperature, (b) a discussion of depolarization effects and their influence on the approach to saturation, and (c) a discussion of the dependence of the magnetic moment measurements on sample positioning errors.