Spin-resolved appearance potential spectroscopy investigations on Fe/Cu(001) overlayers

The theoretical description of spin-resolved appearance potential spectroscopy (SR-APS) developed recently to deal with bulk transition-metal systems has been extended to free surfaces of ${\mathrm{Fe}}_n/\mathrm{Cu}\mathrm{}\left(001\right).$ Results of previous experimental work on fcc-Fe on top of a Cu(001) substrate were interpreted to indicate the coexistence of a few ferromagnetically coupled Fe layers on top of nonferromagnetic Fe layers for $T=110\mathrm{}$ K. Recent theoretical work, on the other hand, found for $n>\mathrm{}2\mathrm{}$ that the ground-state of this system corresponds to antiferromagnetically coupled Fe layers. In order to clarify this situation the SR-APS spectra of ${\mathrm{Fe}}_n/\mathrm{Cu}\mathrm{}\left(001\right)\mathrm{}$ have been calculated assuming the metastable ferromagnetic (FM) as well as antiferromagnetic (AFM) configuration. While for the FM configuration pronounced deviations from experiment were found, a nearly perfect agreement was obtained for the AFM ground-state configuration. This means that the experimental SR-APS spectra are not in conflict with the theoretical prediction but, on the contrary, they strongly support it.