ABSTRACT
This chapter reviews the development of magnetic sensors based on magnetic tunneling junctions (MTJs). The physics of magnetic quantum tunnelling dictates that MTJ can function up to multiple gigahertzes. MTJ is truly nature’s gift, containing a treasure trove of rich physics and promises of applications; so much so that shortly after its discovery, MTJ has taken a large market share in the read/write heads of the data storage industry. MTJ sensors represent the latest magnetic sensor technology with several intrinsic advantages. The performance parameters used to characterize any magnetic sensor are also applicable to MTJ sensors, although the latter have some unique parameters. An MTJ stack is a multilayer deposited on thermally oxidized silicon substrates using dc and radiofrequency sputtering. The field detectability of a magnetic sensor is determined by the intrinsic noise of the MTJ. In MTJs, high temperatures can cause interlayer diffusion and degradation of the barrier, affecting sensor performance.
