Electronic structure and magnetism of one-dimensional Fe monatomic wires on Au(788) investigated with ARPES and XMCD

In this study of fabricated one-dimensional (1D) monatomic Fe wires on a Au(788) substrate, electronic and magnetic features are investigated by angle-resolved photoemission spectroscopy (ARPES) and x-ray magnetic circular dichroism (XMCD). The ARPES spectra show little dispersion both in the parallel and perpendicular directions to the wires revealing a strongly localized nature of the Fe 3d electrons. Finite intensity of the XMCD signals has angular dependence reflecting an anisotropic feature of the localized magnetic moments with an easy axis perpendicular to the substrate. Temperature and field dependence of the XMCD signals shows superparamagnetic behavior well described by the 1D Ising model exhibiting large hysteresis below the blocking temperature, which is ruled by the anisotropy energy. Increase of the average size of the spin blocks with reduced temperature enhances the dramatic change of the magnetic properties of the 1D spin system from soft to hard within a narrow temperature range.