Magnetic Chiral Dichroism Studies using Energy Filtered Images
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1026-C13-06
Magnetic Chiral Dichroism Studies using Energy Filtered Images Benedicte Warot-Fonrose, Christophe Gatel, and Florent Houdellier CEMES-CNRS, 29 rue jeanne Marvig, BP 94347, Toulouse, 31055, France ABSTRACT We present the quantitative measurement of inelastic intensity distributions in diffraction patterns with the aim of studying magnetic materials. The original idea of using inelastic signal in a transmission electron microscope to measure magnetic information has been proposed recently by Schattschneider et al [1] and various experimental set-ups can be imagined [2,3]. We focus on a new experimental configuration which we use to acquire and collect a map of the signal with a high signal-to-noise ratio. We will also present the numerical treatments that need to be performed to get spatially accurate information and energy resolution. We will illustrate our method studying iron single crystal and discuss the effects of the drift and nonisochromaticity corrections. INTRODUCTION Trends in electronics propose the use of spin instead of charge as an information unit. These new spintronic devices are based on magnetic and non-magnetic thin layers through which electrons travel and are scattered or filtered at interfaces depending on their spin. The spin mean free path depends on the material but can be estimated to be in the 100 nm range. The interesting devices for spintronics have therefore dimensions close to few hundred of nanometer and therefore physical measurements have to be performed at this scale. One of the important properties is the local magnetic moment and its evolution close to surfaces or interfaces. X-ray magnetic circular dichroism has been a powerful technique to measure magnetic moments on µm size areas. However new set-ups need to be built now to take into account the reduced size of the regions of interest. Experimental techniques capable of measuring the magnetic moment at this scale are developed, especially photo emission electron microscopy (PEEM, [4]). This technique is very promising but needs synchrotron radiation. The nanometer size of the probe in a transmission electron microscope (TEM) is compatible with the resolution needed for magnetic measurements on spintronic devices. Hébert et al. [5] proposed an original set-up to combine the precise location of the probe in a TEM and the measurement of magnetic properties. This technique, called energy-loss magnetic chiral dichroism EMCD, is based on the distribution in the diffraction plane of the inelastically scattered electrons that have crossed the magnetic sample. The signal is detected with an electron energy loss spectrometer to probe the inelastic interactions. The major issue in these experiments is the very low signal. Therefore experimental acquisitions have to be optimized to get a reliable signal. Many experimental solutions have been proposed [2, 3]. We will present a new experimental set-up using the spherical aberration corrector that we have used [6] and the post-treatments we have developed to obtain trustworthy d
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