Stretchable Spin Valve with Stable Magnetic Field Sensitivity by Ribbon-Patterned Periodic Wrinkles

Abstract

A strain-relief structure by combining the strain-engineered periodic wrinkles and the parallel ribbons was employed to fabricate flexible dual spin valves onto PDMS substrates in a direct sputtering method. The strain-relief structure can accommodate the biaxial strain accompanying with stretching operation (the uniaxial applied tensile strain and the induced transverse compressive strain due to the Poisson effect), thus significantly reducing the influence of the residual strain on the giant magnetoresistance (GMR) performance. The fabricated GMR dual spin-valve sensor exhibits the nearly unchanged MR ratio of 9.9%, magnetic field sensitivity up to 0.69%/Oe, and zero-field resistance in a wide range of stretching strain, making it promising for applications on a conformal shape or a movement part.

Magnetization Manipulation of a Flexible Magnetic Sensor by Controlled Stress Application

“…For magnetic devices, the effects of strain on flexible magnetic memory 9–11 and sensors 12–14 as well as on a single magnetic layer have also been studied 15,16 . Therefore, zig-zag or wrinkled types and pre-strained structures have been suggested to reduce the influence of external stress and to make devices robust against large strain 14,17–20 . On the other hand, since magnetic materials have inverse magnetostriction effect, i.e., a magnetization change induced by external stress, additional attention should be paid to mechanical effects.…”

Flexible Sensors—From Materials to Applications

“…Micrometre thick sensors (1.145 µm) based on metal thin films could function when wrapped around a hair [366]. However, metal thin film-based devices tend to have limited stretchability (10%) [44,[365][366][367][368][369], therefore they are not well suited for wearable and body motion monitoring applications [362,363,406]. Highly stretchable resistive type strain sensors have been developed using mechanisms such as crack propagation in thin films or the disconnection/tunnelling effect between conductive fillers [362,363].…”

“…Magnetic sensors were generally fabricated using stacked thin films deposited on a flexible substrate. Flexible magnetic sensors based on giant magnetoresistance (GMR) [492][493][494][495], anisotropic magnetoresistance (AMR) [496,497], hall sensors [319,498,499], spin valve [368,500], tunnelling magnetoresistance (TMR) [501,502], and magnetoimpedance (MI) were developed [503]. The most important parameters for flexible magnetic field sensors are sensitivity, magnetic field direction and bendability.…”

Assembly and Self‐Assembly of Nanomembrane Materials—From 2D to 3D

“…Recently, researchers have assembled waved magnetic sensor after transferring the entire device to elastic substrate . The morphology of the sensor made from [Co/Cu] 50 multilayer nanomembrane after formation of wavy structure is displayed in panel (i) of Figure d.…”