Highly sensitive spintronic strain-gauge sensor based on a MgO magnetic tunnel junction with an amorphous CoFeB sensing layer

Abstract

We investigated spintronic strain-gauge sensors (Spin-SGSs) based on magnetic tunnel junctions (MTJs). To enhance the strain sensitivity of Spin-SGSs, which is defined as the gauge factor = (ΔR/R)/Δε, we investigated MgO-MTJs with an amorphous CoFeB sensing layer that exhibits high magnetostriction and soft magnetic properties. To maintain the amorphous structure of the CoFeB sensing layer even after post annealing, we applied a MgO capping layer (MgO-cap) to the CoFeB sensing layer and compared it with a Ta capping layer (Ta-cap). After post annealing at 320 °C, the CoFeB sensing layer with a MgO-cap maintained a low coercivity of 3 Oe, whereas that with a Ta-cap exhibited a high coercivity of 25 Oe. Microstructure analysis revealed that the CoFeB sensing layer with the MgO-cap has an amorphous structure because boron remains in the CoFeB sensing layer even after post annealing. The gauge factor for the Spin-SGS with the MgO-cap was 4016, which was four times larger than 942 for the Spin-SGS with the Ta-cap.

Tunneling Magnetoresistance Transition and Highly Sensitive Pressure Sensors Based on Magnetic Tunnel Junctions with a Black Phosphorus Barrier

“…In addition, the pressure sensitivity is described by the gauge factor: GF = ( ΔR / R )/ Δε , where ΔR / R is the relative change in resistance and Δε is the relative change in strain. Subsequently, a certain amount of research effort has been devoted to improve the performances, especially the GF, of such pressure sensors. − These works have initiated a new research direction for both MTJs and pressure sensors and indicate that the pressure sensors based on MTJs have great potential to satisfy the requirements mentioned above. However, owing to the working mechanism, this type of pressure sensor can only measure the shear pressure and is not applicable to the measurement of normal pressure.…”

Investigation of Multilayer Nanostructures of Magnetic Straintronics Based on the Anisotropic Magnetoresistive Effect

“…The figure clearly shows that when a compression load is applied to the sample along the EMA, the coercivity of the nanostructure changes from 1.3 Oe to 2.4 Oe. The change in the loop of the axis of hard magnetization (HMA) and its partial reversal to the EMA can be explained by the appearance of magnetic anisotropy induced by mechanical stress [2]. During the compression load along the HMA, the coercivity of the nanostructure increased from 15.8 Oe to 17.1 Oe, and the loop did not change.…”

“…The market for combined sensors, transducers and MEMS is predicted by Marketwatch to grow by an average of 11.74% by 2025. This forecast is based on an increase in global demand for portable and wearable devices; in addition, demand for combined microelectronic devices will increase in the consumer markets: electronics, Internet of smart things (IoT), automotive, healthcare, aerospace and defense industries [1][2][3][4][5]. According to estimates, the market for magnetosensitive transducers by 2027 will reach a value of USD~4.7 billion, with an increase over the forecast period by an average of 6% [6].…”

“…Of greatest interest is a nanostructure with a magnetic tunnel junction on MgO and the effect of mechanical stress on its properties [2]. In [17], the results of theoretical and experimental studies of the tunnel junction with CoFeB/MgO/CoFeB were presented.…”

Manipulation of Magnetic Properties and Magnetoresistance in Co/Cu/γ′-Fe4N/Mica Flexible Spin Valves via External Mechanical Strains

“…Due to their anisotropy magnetoresistance (AMR), tunneling magnetoresistance (TMR), − giant magnetoresistance (GMR), − spin–orbit torque, and the planar Hall effect, flexible spintronic devices have attracted much attention. Flexible spin valves (SPVs) are some of the components of flexible sensors and spintronic devices .…”