Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 71: Surface Magnetism (jointly with MA)

O 71.1: Hauptvortrag

Donnerstag, 14. März 2013, 15:00–15:30, H3

Spin-polarized scanning field emission microscopy and spectroscopy — •Anika Schlenhoff — Institute of Applied Physics, University of Hamburg

High electric fields can discharge electrons from a solid, thereby generating an emission current, which becomes spin-polarized when using a magnetic emitter. A very local injection of these electrons is achieved when approaching a magnetic tip to a sample in an SP-STM setup, and scanning allows for magnetic imaging by means of spin-polarized emission conductivity measurements. Although field emission is routinely used for microscopy purposes, the question remained open how it affects magnetism on the local scale. A detailed understanding of the interplay of hot-electron spins with magnets is essential for the interpretation of many hot electron spin phenomena and characterization techniques, as well as for applications in spintronic devices.

Here we show that a spin-polarized field-emission current resonantly injected into magnets, consisting of only about 50 iron atoms on a W(110) surface, generates considerable Joule heating and spin-transfer torque, thereby severely affecting the thermally driven magnetization reversal. The switching frequency is increased due to phonon generation, and a lifetime asymmetry develops with increasing emission current, most likely driven by Stoner excitations. Even magnetization reversal of quasistable nanomagnets can be triggered by spin-polarized field-emission. Our experiments demonstrate the capability of spin-polarized scanning field emission microscopy for magnetic observation and controlled manipulation on the atomic scale at nm distances.