Picotesla Magnetic Sensors for Low-Frequency Applications

Abstract

We demonstrate a simple low-power, magnetic sensor system suitable for high-sensitivity magnetic-field mapping, based on solid-state magnetic tunnel junction devices with minimum detectable fields in a 100 pT range at room temperature. In this paper, we discuss a method that uses multilayer thin films to improve the performance of the soft ferromagnetic layer in magnetoresistive sensor applications, by reducing the coercivity and/or improving the reversibility. We have used it in the design of our new magnetic sensor. This sensor has a sensitivity as high as 750%/mT. The magnetic sensor only dissipates 1 mW of power while operating under an applied voltage of 1 V.

Yoke-shaped MgO-barrier magnetic tunnel junction sensors

“…28 Better values of field detectivity have only obtained in this way. [29][30][31][32] For example, Chaves et al have reported a value of field detectivity of 51 pT= ffiffiffiffiffiffi Hz p at 30 Hz and field sensitivity of 870%/ mT by using a flux concentrator. 29,30 The relation of magnetic field, field sensitivity, and field detectivity is plotted in Figure 4(b).…”

Linearization strategies for high sensitivity magnetoresistive sensors

“…The inclusion of NiFe directly after CoFeB strongly reduces TMR due to the texture propagation from NiFe (fcc 1 1 1) to CoFeB (bcc 1 0 0) [61]. Correct crystallography can be assured introducing a thin Ta dusting layer (∼0.21 nm) between these layers.…”

A non-erasable magnetic memory based on the magnetic permeability

“…The fabrication of these MTJ was done as follows: First, a multilayer stack was deposited onto a thermally oxidized silicon substrate in a magnetron sputtering system with a base pressure of 5 Â 10 MgO insulator comprise the free layer, and the three layers below are part of the synthetic antiferromagnetic (SAF) reference layer [26]. Optical lithography was used to pattern a chain of ten 40 Â 10 μm MTJ ellipses with each major axis aligned along the chain length.…”