X-ray magnetic circular dichroism in reflection geometry: A tool for investigating surface magnetism in thin films

Surface and interface magnetisms in oxide thin films and heterostructures have been a recurrent topic during the past years due to their relevance in the implementation of magnetoelectronic devices. Magneto-optical techniques, such as x-ray magnetic circular dichroism, turn out to be a very efficient tool to study surface magnetism due to their sensitivity to magnetic and chemical variations across the sample depth. Nevertheless, the application of the sum rules for the determination of the spin magnetic moment might lead to uncertainties as large as 40%. To overcome this problem we present an alternative approach consisting in using x-ray magnetic circular dichroism in reflection geometry. Data analysis by using a computer code based on a 4×4 matrix formalism indicates that surface and interface roughnessas are of major relevance for a proper description of the experimental data and a correct interpretation of the results. By using such an approach, we discuss the presence of a narrow surface region with strongly depressed magnetic properties in La2∕3Ca1∕3MnO3 thin films.