CD Laboratory for Advanced Magnetic Sensing and Materials

Sensors based on magnetic resistance changes are currently state of the art in hard discs. Detailed computer simulations are being worked on in order to be able to extend this technology to applications in the automotive sector and in the biological/medical field.

The research focus of this laboratory is on GMR and TMR sensors (giant magnetoresistance, GMR and tunnel magnetoresistance, TMR).

GRM sensors are based on the phenomenon of giant magnetoresistance, for the discovery of which the Nobel Prize in Physics was awarded in 2007. They utilise the fact that the electrical conductivity of materials also depends on their magnetic orientation. In special layered systems made of different materials, electrons can only pass through the layers if the directions of magnetisation are aligned exactly correctly. If this is not the case, the layers block the path and a giant magnetoresistance (GMR) occurs.

TMR sensors are also based on a layer system in which there is a non-magnetic layer between two magnetic layers. They utilise the quantum mechanical phenomenon of magnetic tunnel resistance.

GMR and TMR sensors have a high sensitivity and a 360° angular resolution. Their application works very well, but there is still a lack of basic knowledge about the actual processes in the fine layers

The research work of this CD Laboratory is based on special software developed at the Institute of Solid State Physics at the Vienna University of Technology to describe the magnetic properties of materials. It is used by leading hard drive manufacturers for the optimisation and design of GMR read heads in hard drives.

This software is now to be expanded for use in the automotive industry and for biological/medical sensors. Specifically, this involves, for example, measurements in speed systems such as the ABS system or the determination of pathogens or cancer diagnostics. This is not as simple as one might expect, as the structures to be analysed are much "larger": while hard disk technology works in the nanometre range, the automotive sector works in the micrometre range. For simulations, the number of unknowns is therefore at least a factor of 1000 higher. Innovative and new modelling concepts are needed to solve this problem.

To this end, research is being conducted into new mathematical solutions and algorithms, such as highly parallel simulation methods and the use of graphics processors to achieve higher performance (GPU computing).

The new software developed should be able to do the following things:

-Development of a detailed understanding of current GMR and TMR sensors

-Development of new functional structures

-Development of simplified simulations that companies can use to test the interaction of electronic components (resistors, transistors, etc.) with the GMR and TMR sensors.

Based on the detailed computer simulations, it should be possible to make predictions about the behaviour of the sensors and suggest new designs - and thus ultimately help to reduce the development times and costs for new sensors.