The Physics Colloquium is a series of lectures at the Institute of Physics. This week, our guest lecturer Dr Timo Kuschel will be presenting his current research work:
The determination of structural, chemical and magnetic properties of magnetic multilayers is important for investigating magnetic heterostructures that are utilized, e.g., for spin transport experiments. Especially the interface and, more general, the depth-resolved properties should be known when discussing how well a spin current can pass the individual layers and interfaces. Here, non-destructive experimental approaches based on x-ray reflectivity and spectroscopy techniques are the key to studying exactly the same sample that is used for spin transport investigations. Even the magnetization dynamics can be analyzed layer-resolved based on the presented approaches.
I will discuss three depth profiling techniques along with three research directions of our group:
1) Oxidic depth profiling via x-ray photoelectron spectroscopy (XPS):
We use ionic liquid gating to manipulate the oxidic content of magnetic multilayers and, thus, alter the magnetic properties [1]. In order to identify the oxidic depth profile, we developed a new approach based on XPS and a combined analysis of spectra at multiple energy regions [2].
2) Magnetic depth profiling via x-ray resonant magnetic reflectivity (XRMR): The interface properties of Pt layers, which are used for spin current detection, can be magnetically altered by the so-called magnetic proximity effect. Here, we study the magnetic interface properties of Pt by synchrotron-based XRMR element-selectively [3] and obtain the quantitative static magnetization depending on the depth of the sample [4]. In addition, we can use XRMR to study the magnetic depth profile cation- and lattice-site-selective as shown for the magnetic termination of Fe3O4 layers [5].
3) Magnetization dynamics depth profiling via x-ray detected ferromagnetic resonance (XFMR): XFMR uses time-resolved x-ray magnetic dichrosim to trace the spin precession that is excited by ferromagnetic resonance [6]. This synchrotron-based and element-selective technique allows to identify a spin current that passes, e.g., an antiferromagnetic insulator [7].
