Spin tranfer torque effects in metallic multilayers and tunnel structures
Funding: BMBF, FKZ 13N10144
The spin-transfer-torque (STT) effect was discovered as a side effect in GMR multilayer elements. Nowadays it represents a promising approach towards switching of magnetic bits by means of electric current or the creation of electromagnetic waves due to current driven oscillations of the magnetisation. Prerequisite for such devices are nanoscale multilayer elements with a diameter below 200 nm. GMR and TMR, i.e. magneto-resistance elements allow the read out of the stored information via the electric resistance and not the magnetic stray field. Our project deals with the fabrication of such elements by means of thin film deposition and electron beam Lithography as well as understanding the generated oscillations of the magnetization and the switching process.. For the latter the Landau-Lifshitz-Gilbert equation will be applied which describes the time dependent behaviour of the magnetization and the STT effect.
Nanopillar based on a TMR multilayer (exemplarily) along with the switching behaviour of the magneto-resistance
Left: TEM Cross section of a electrically contacted TMR nanopillar
Right: Electron microscopy of a free-standing nanopillar
Left: Hysteresis loops of the magneto resistance vs. dc current dependent on the external magnetic field.
Right: Dependence of the critical switching current on the external magnetic field