Magnetic and structural properties of ultra-short 1D ferromagnetic chains*

The magnetic properties of 1D Fe and varying composition Fe/Co chains are studied as a function of chain length and structural composition. Ultra-short chains, ~7 to 400 atoms long, can be grown by organic molecular beam epitaxy using Metallo-Phthalocyanine (MPc) superlattices (SLs). The orientation of the chains can be controlled by the appropriate choice of substrate whereas their length and composition can be controlled by the SL structure. Furthermore, the magnetic signal of ultra-short chains can be amplified by increasing the periodicity of the SL, which enables the use of conventional techniques such as VSM and SQUID to study their magnetic properties. In this work, we discuss the magnetic behavior of ultra-short 1D Fe chains as a function of length and composition. We have found that the coercive field decreases when the length of the chains is reduced from 400 to 7 atoms long. We correlate the observed magnetic behavior with structural information obtained from x-ray diffraction and refinement.