Magneto-Resistive Sensing with Ultra-High Resolution by Using a Focused Magnetic Field
Publication Date: 2014-Aug-20
The IP.com Prior Art Database
In magneto-resistance (MR)-based nanoscale position sensing, the change in position of a magnetic field source relative to an MR sensor can be measured as a change in electrical resistance of the MR sensor. The shape and strength of the magnetic field produced by the magnetic field source substantially determines the achievable sensitivity and resolution. As the magnetic field source and the sensor are scaled down, the resolution improves. However, downscaling of the magnetic field source while keeping high magnetic field gradients is challenging. Here, we present a new sensing concept comprising a magneto-resistive sensor, a source of magnetic field such as a permanent magnetic dipole or a solenoid and a provision for focusing the magnetic field of the magnetic source by means of a nano-fabricated flux concentrator. By using the nano-fabricated flux concentrator, the magnetic field of the magnetic source can be focused and shaped with an extremely high precision enabled by today's nanofabrication processes such that it affects the sensing element with desired strength and gradient.
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Magneto-Resistive Sensing with Ultra -High Resolution by Using a Focused Magnetic Field
High bandwidth, high resolution nanoscale sensing is a key enabling technology for nanoscale science and engineering. Application areas include life sciences, scanning probe microscopy, semiconductor fabrication and material science.
Currently available position sensors based on optics, capacitors and inductive coils, although accurate and fast, do not scale down to micro-scales for use in micro-structures or in large-scale point-wise position sensing of macro-structures. Thermo-electric position sensors, on the other hand, easily scale down to micro-scale, but suffer from low resolution and bandwidth.
A position sensing concept based on the property of magneto-resistance (MR) was introduced in [1,2]. Magneto-resistance is the property with with the electrical resistance of a thin layer of conductive layer sandwiched between ferromagnetic layers changes as function of the applied magnetic field [3,4]. An MR-sensor uses this property to sense the magnetic field. In , a scheme was proposed whereby the motion of a positioner was translated to a change in the magnitude of magnetic field as seen by an MR-sensor. This scheme has a potential to address the challenge of high bandwidth, low noise sensing in a variety of applications in nanotechnology.
In , we proposed a method to achieve high sensitivity and resolution using a MR-sensor and a magnetic dipole. It follows from  that to reach high sensitivity and resolution, the magnetic dipole has to be extremely thin, with dimensions comparable to the size of the sensor. With very small sensors and high sensitivities desired, it can be challenging to manufacture such magnetic dipoles in a direct way from the common magnetic alloys. This disclosure presents a new concept to circumvent this problem which is based on focusing the magnetic field of the magnetic dipole.
 H. Pozidis et al., "Magneto-resistance based nano-scale position sensor", United States Patent Application No. US2010/0085041A1, 2010.
 V. Kartik, A. Sebastian, T. Tuma, A. Pantazi, H. Pozidis, and D. Sahoo, "High- bandwidth nanopositioner with magneto-resistance based position sensing," Mechatronics, 2011.
 S. Parkin, X. Jiang, C. Kaiser, A. Panchula, K. Roche, and M. Samant, "Magnetically engineered spintronic sensors and memory," Proceedings of the IEEE, vol. 91, no. 5, pp. 661-680, 2003.
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 J. Daughton, "Spin-dependent sensors,"" Proceedings of the IEEE, vol. 91, no. 5, pp. 681-686, 2003.
This disclosure presents a new sensing concept comprising a magneto-resistive sensor, a source of magnetic field such as a permanent magnetic dipole or a solenoid and a provision for focusing the magnetic field of the magnetic source by means of a nano-fabricated flux concentrator. By using the nano-fabricated flux concentrator, the magnetic field of the magnetic field source can be focused and shap...