Considering non-uniform current distributions in magnetoresistive sensor designs and their implications for the resistance transfer function

TL;DR

This paper investigates how non-uniform current distributions in disk-shaped spin valves affect their resistance transfer function, highlighting the influence of magnetic states and electrode placement on device performance.

Contribution

It introduces a detailed analysis of conductive and geometric inhomogeneities in spin valves, revealing their impact on resistance-magnetization relationships.

Findings

Non-uniform current distributions cause deviations in resistance readings.

Electrode placement significantly influences the resistance transfer function.

Comparison with measurements validates the theoretical models.

Abstract

Non-uniform current distributions of spin valves with disk shaped free layers are investigated. In the context of spin valves, the vortex state, which is the ground-state in many disk shaped magnetic bodies, allows for distinct parallel channels of high and low resistivity. The readout current is thus able to evade high resistivity regions in favor of low resistivity regions, giving rise to 'conductive inhomogeneities'. Therefore, the total resistance of the spin valve does not always correspond exactly to the total average magnetization of the free layer. In addition, the resistance transfer function can be significantly influenced by the spatial placement of the electrodes, giving rise to 'geometric inhomogeneities'. The resulting deviations from resistance to magnetization transfer function are investigated for different spin valve geometries and compared to measurements of comparable devices.