Magnetic behavior of Fe atoms on the surface of palladium

Abstract

The magnetic properties of thin Pd films with Fe surface impurities are investigated by means of the anomalous Hall effect (AHE). The AHE measures the $z$ component (perpendicular to the surface) of the magnetization and is sufficiently sensitive to investigate Fe coverages down to 0.01 atomic layers (atola). The magnetization varies strongly nonlinearly with magnetic field. For small Fe coverages, in the range from 0.01 to 0.1 atola the susceptibility is temperature independent. The author concludes that the Fe has lost its moment and represents a local spin-fluctuating system. For Fe coverages above 0.5 atola the magnetization shows a hysteresis which disappears with increasing temperature. In this range of coverage the Fe atoms possess a magnetic moment. The moments prefer the orientation perpendicular to the film and form an Ising ferromagnet. In the intermediate range around 0.3-atola Fe the susceptibility follows a Curie law. The large value of the susceptibility either requires the existence of super large moments of about $100{\mu }_B$ or is due to an indirect exchange enhancement of the magnetic field. Covering the dilute Fe-surface atoms with a few layers of Pd changes the magnetic behavior of the Fe completely. The magnetization follows a Brillouin function with $S=8\mathrm{}$ and $g=2\mathrm{}$ and describes the magnetization of free giant moments.