Quantifying the crossover from surface to bulk properties in important spintronic materials

Figure 1: Top: photoelectron spectroscopy measurements of La0.67Sr0.33MnO3. The narrow “well-screened peaks” marked by the black arrows are interpreted as a signature of the metallic behaviour, and are much more pronounced in the most bulk-sensitive measurement (orange curve). Bottom: schematic of the depth-profiling effect of changing the photon energy. Credit: Diamond Light Source

The expanding field of spintronics promises a new generation of devices by taking advantage of the spin degree of freedom of the electron in addition to its charge to create new functionalities not possible with conventional electronics. The giant magnetoresistance (GMR) effect (2007 Nobel Prize in Physics) is a paradigmatic example of a spintronics application. As the interface between the magnetic and non-magnetic materials is a key component of any such device, it is crucial to characterise and understand both the surface and bulk electronic and magnetic properties.

In a recent publication in Nature Communications, a joint venture between theorists, experimentalists and sample growers led by a group from National Research Council (CNR) Trieste, Italy, reports a systematic photoemission spectroscopy study of two representative for spintronics applications, (Ga,Mn)As and La1-xSrxMnO3. Using the photon energy of the incident synchrotron radiation from the Surface and Interface Structural Analysis beamline (I09) at Diamond Light Source as a depth-profiling tool, they were able to quantify the variation in the strength of the magnetic order and the electrical conduction from the down into the bulk of the material. This study establishes the different properties of the surfaces compared with the bulk and the characteristic ‘critical’ depths needed…

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