Magnetoresistive Sensor Detectivity: A Comparative Analysis

TL;DR

This paper compares the noise and detectivity of GMR and MTJ magnetic sensors, revealing trade-offs in noise performance, linear range, and potential upper limits based on current TMR values.

Contribution

It introduces a scaling method to compare sensor detectivity across different linear ranges and assesses the upper performance limits of MTJ sensors with record TMR values.

Findings

GMR sensors have lower noise and detectivity but smaller linear range.

Scaling linear ranges equalizes low-frequency detectivity between GMR and TMR sensors.

The technique estimates the maximum potential of MTJ sensors with current TMR records.

Abstract

We report on the noise performance characteristics of magnetic sensors using both magnetic tunnel junction (MTJ) and giant magnetoresistance (GMR) elements. Each sensor studied has a notably different noise and detectivity. Of the sensors we measured, those based on GMR multilayers have the lowest noise and detectivity. However, the GMR sensor also has a significantly smaller linear range. To make a direct comparison between sensors we scale the linear operating ranges of each sensor to be the same. This is the phenomenological equivalent of modifying the flux concentration. Upon scaling the low frequency detectivity of the TMR sensors becomes essentially equal to that of the GMR sensor. Using the scaling approach we are able to place the detectivity in the context of other key parameters, namely size and power consumption. Lastly, we use this technique to examine the upper limit for magnetoresistive sensor performance based on a notional MTJ sensor using present record setting TMR values.