Element-specific magnetometry with photoelectron dichroism: FeCo and FeNi

Abstract

We have investigated fcc Fe x Co 1− x and Fe x Ni 1− x alloys grown on Cu(1 0 0) with X-ray magnetic linear dichroism angular distributions in photoemission (XMLDAD). To achieve this end, a simple model has been developed, which accurately describes the experimental spectra and supports our application of XMLDAD as a form of elementally specific magnetometry. This model combines the simplicity and physical insight of a single-electron picture with multielectronic effects, via the utilization of “Doniach–Sunjic” lineshapes for each component within the Fe 3p multiplet. We will also briefly discuss the observed fine structure in the emission of the Fe 3p core level, which was previously predicted but lacking experimental confirmation. We have found different behavior for the dichroism of the Fe 3p level at high and low Fe concentrations upon alloying with Co, compared to alloying with Ni. These contrasting observations can be explained in part by the different behavior of the atomic volume. Both systems show also a change of the in-plane easy axis upon increasing the Fe content. For small concentrations the easy axis is along the {0 1 1} direction, which changes to the {0 0 1} direction at a higher Fe content. Interestingly the actual transition occurs in both instances at roughly the same electron/atom count.