Impact of external magnetic fields on STT-MRAM

TL;DR

This paper examines how external magnetic fields affect STT-MRAM operation, concluding that typical environmental magnetic fields do not impair its functionality, based on extensive industry experience and field measurements.

Contribution

It provides an analysis of magnetic field sources and magnitudes relevant to STT-MRAM, demonstrating its magnetic immunity in typical use environments.

Findings

Magnetic immunity of STT-MRAM is sufficient for most applications.

External magnetic fields during normal operation do not significantly affect STT-MRAM.

Handling precautions are mainly needed to avoid high magnetic fields during chip handling.

Abstract

This application note discusses the working principle of spin-transfer torque magnetoresistive random access memory (STT-MRAM) and the impact that magnetic fields can have on STT-MRAM operation. Sources of magnetic field and typical magnitudes of magnetic fields are given. Based on the magnitude of commonly encountered external magnetic fields, we show below that magnetic immunity of STT-MRAM is sufficient for most uses once the chip is mounted on a printed circuit board (PCB) or inserted in its working environment. This statement is supported by the experience acquired during 60 years of use of magnetic hard disk drives (HDD) including 20 years of HDD with readers comprising magnetic tunnel junctions, 20+ years of use of magnetic field sensors as position encoders in automotive industry and 15+ years of use of MRAM. Mainly during chip handling does caution need to be exercised to avoid exposing the chip to excessively high magnetic fields.