Site-Specific Mössbauer Evidence of Structure-Induced Magnetic Phase Transition in fcc Fe(100) Thin Films

The magnetic phases of fcc Fe(100) in $\mathrm{Fe}\left(100\right)/{\mathrm{Cu}}_{1-x}{\mathrm{Au}}_x\left(100\right)$ multilayers with lattice parameters in the range $a=3.606$ to 3.704 Å have been studied using Mössbauer spectroscopy and SQUID magnetometry. The Fe layers have a two-phase structure consisting of a low-spin antiferromagnetic (AF) and a high-spin ferromagnetic (FM) phase. The average Fe moment and the relative population of FM Fe both increase with $a$, but the hyperfine magnetic field for the FM phase is not dependent on $a$, indicating that the increase in moment comes only from the FM phase population increase.