Linearization strategies for high sensitivity magnetoresistive sensors

¹ Instituto de Engenharia de Sistemas e Computadores – Microsistemas e Nanotecnologias, 1000 Lisboa, Portugal
² Instituto Superior Tecnico, Physics Department, Universidade de Lisboa, 1049 Lisboa, Portugal
³ International Iberian Nanotechnology Laboratory, 4715 Braga, Portugal

^a e-mail: scardoso@inesc-mn.pt

Received: 17 April 2015
Revised: 28 July 2015
Accepted: 31 August 2015
Published online: 5 October 2015

Abstract

Ultrasensitive magnetic field sensors envisaged for applications on biomedical imaging require the detection of low-intensity and low-frequency signals. Therefore linear magnetic sensors with enhanced sensitivity low noise levels and improved field detection at low operating frequencies are necessary. Suitable devices can be designed using magnetoresistive sensors, with room temperature operation, adjustable detected field range, CMOS compatibility and cost-effective production. The advent of spintronics set the path to the technological revolution boosted by the storage industry, in particular by the development of read heads using magnetoresistive devices. New multilayered structures were engineered to yield devices with linear output. We present a detailed study of the key factors influencing MR sensor performance (materials, geometries and layout strategies) with focus on different linearization strategies available. Furthermore strategies to improve sensor detection levels are also addressed with best reported values of ∼40 pT/√Hz at 30 Hz, representing a step forward the low field detection at room temperature.