Magnetic dead layers in La2/3Ca1/3MnO3 thin films probed by X-ray magnetic circular dichroism in reflection

TL;DR

This study uses reflection X-ray magnetic circular dichroism to accurately analyze surface magnetic dead layers in La2/3Ca1/3MnO3 thin films, revealing a narrow region with suppressed magnetism.

Contribution

It introduces a reflection geometry approach with matrix formalism to better interpret surface magnetism, overcoming uncertainties of traditional sum rule methods.

Findings

Identification of a narrow surface region with depressed magnetic properties.

Surface and interface roughness significantly affect magnetic measurements.

The method provides more realistic estimates of surface magnetism.

Abstract

Surface magnetic properties of perovskite manganites have been a recurrent topic during last years since they play a major role 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% in case of Mn ions. To overcome this problem we present an alternative approach consisting of using X-ray magnetic circular dichroism in reflection geometry. Fit of the data by using a computer code based in a 4X4 matrix formalism leads to realistic results. In particular, we show that surface and interface roughness 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 demonstrate the presence of a narrow surface region with strongly depressed magnetic properties in La2/3Ca1/3MnO3 thin films.