In situ resistance and magnetoresistance experiments on spin orbit torque systems

• Applicant: Professor Dr. Günter Reiss
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 366210174

In this project, we want on the one hand to establish in-situ measurements of the electric resistance, the magnetoresistance and the anomalous Hall effect in an evaporation- and a sputter-chamber. The measurements will be done during the growth of single layer films and of multilayers that are known as spin orbit torque systems. The spin orbit torque uses the accumulation of spins driven by, e.g., the spin Hall effect to switch the magnetisation of non-symmetric multilayers made from non-magnets and ferro- or ferrimagnets. This technique is extremely promising for future electronic device. In addition, it is of basic interest because the systems used show a locking between the momentum of the charge carriers and their spin.On the other hand, we want to evaluate in detail the spin Hall angle and the spin orbit torque switching for the samples that have been characterised by the in-situ measurements. From these in-situ experiments, the resistivities of the individual layers can be determined as first quantity. Moreover, it is possible to analyse the resistance increase when a metal A is covered by a metal B and to draw conclusions on the strength of the scattering of the charge carriers at the interface between A and B.These informations are at present not available for the interpretation of experiments on spin orbit torque. The resistivities of the individual layers are often taken from data of bulk materials, and large errors are commonly accepted. Moreover, the relation between the size of the spin Hall angle and the scattering of the charge carriers at the interfaces is an open and very important question. We hope, that our research in this project can contribute to the following scientific questions:- Which current flows in the individual layers?- How strong is the scattering of the electrons at the interfaces?- How do the effects (spin Hall, spin orbit torque, anomalous Hall effect, SMR, USMR, ..) depend on the thicknesses of the individual layers and the quality of the interfaces?- Is there a correlation between the strength of the spin orbit torque and the interface scattering of the charge carriers?

• DFG Programme: Research Grants