Magnetic Sensor Phase-Locked Oscillation Noise Reduction
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Solution Overview
Problem
Magnetic sensors face challenges in achieving high signal-to-noise ratios due to magnetic thermal noises, particularly in micro magnetic oscillation elements, where processing fine pillar-like structures is difficult and noise increases with finer dimensions.
Innovation Solution
A magnetic sensor design featuring a magnetic oscillation element with a fixed magnetization layer, a magnetization oscillation layer, and a non-magnetic layer, where two oscillation elements interact to achieve a phase-locked state, reducing oscillation line widths and enhancing signal resolution without requiring complex processing of the magnetization oscillation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the tunnel insulation layer is made thinner to reduce tunneling resistance and suppress shot noise, then the signal magnitude increases, but the manufacturing precision becomes drastically difficult to achieve and shorting between electrodes becomes more likely
Solution Approach 1:
The patent extracts the tunnel insulation layer from the structure by replacing it with a magnetic oscillation element configuration. Instead of using a thin Al-O tunnel insulation layer that requires atomic-layer precision, the invention uses a magnetic oscillation element with a magnetization oscillation layer and fixed magnetization layer separated by a non-magnetic layer, eliminating the need for ultra-thin insulation layer fabrication.
Solution Approach 2:
The patent replaces the electrical tunneling mechanism (mechanical/electrical system) with a magnetic oscillation mechanism. Instead of relying on electron tunneling through a thin insulation layer, the invention uses spin-polarized current-induced magnetization oscillation in a magnetic oscillation element, substituting the physical mechanism to avoid the manufacturing precision problem.
2Productivity
If the element size is reduced to match recording bit size for higher recording density, then the recording density increases, but magnetic thermal noises become more dominant and reduce the signal-to-noise ratio
Solution Approach 1:
The patent employs periodic action by inducing magnetization oscillation in the magnetic oscillation element using spin-polarized current. The magnetization oscillates periodically at a specific frequency, and by detecting this oscillation signal, the system achieves high signal-to-noise ratio even in miniaturized elements, as the periodic oscillation stands out against the background magnetic thermal noise.
Solution Approach 2:
The patent utilizes magnetic vibration by inducing oscillation of magnetization in the magnetic oscillation element. The spin-polarized current causes the magnetization to vibrate at a characteristic frequency, and this magnetic vibration generates a detectable oscillation signal that enhances the signal-to-noise ratio, allowing high-density recording without being limited by magnetic thermal noise.
3Productivity
If complex processing is applied to create fine pillar-like structures for high-density recording, then the recording density increases, but the device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent applies segmentation by dividing the magnetic sensor into distinct functional layers: a fixed magnetization layer, a non-magnetic layer, and a magnetization oscillation layer. This layered segmentation allows each component to be fabricated using standard thin-film deposition techniques without requiring complex pillar-like structure processing, simplifying manufacturing while maintaining high-density recording capability.
Solution Approach 2:
The patent transitions from three-dimensional pillar-like structures to a planar layered structure. Instead of fabricating vertical pillars that require complex etching and deposition, the invention uses a stacked layer configuration where the magnetic oscillation element is formed as a thin-film stack, moving the solution to another dimension (from 3D pillars to 2D layers) and significantly reducing processing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively reduces magnetic thermal noise, allowing for higher signal-to-noise ratios and enabling detection of magnetic fields in microscopic regions without the need for complex processing, thus improving recording density.
Implementation Method 1
a magnetic oscillation element whose oscillation frequency changes depending on the magnitude of an external magnetic field
Implementation Method 2
a first magnetization oscillation layer... for passing current perpendicularly to the film surfaces
Implementation Method 3
A GMR element, such as GMR head, comprises a multi-layer film having a sandwich structure comprising a ferromagnetic layer, a non-magnetic layer, and another ferromagnetic layer. The GMR element utilizes the magneto-resistive effect of what is called a spin-valve film.
Implementation Method 4
TMR elements utilizing the tunneling magneto-resistive effect (TMR effect) are currently being developed to allow magnetic recording at still higher densities
Data Source
AI summary
A magnetic sensor includes a magnetic oscillation element whose oscillation frequency changes depending on the magnitude of an external magnetic field, and an oscillation element provided in the vicinity of the magnetic oscillation element and oscillating at an oscillation frequency close to that of the magnetic oscillation element. The magnetic oscillation element includes a first fixed magnetization layer whose magnetization is fixed, a first magnetization oscillation layer, a first non-magnetic layer provided between the first fixed magnetization layer and the first magnetization oscillation layer, and a pair of electrodes for passing current perpendicularly to the film surfaces of the first fixed magnetization layer, the first magnetization oscillation layer, and the first non-magnetic layer. These two elements are used in combination with the passed current to acquire a high frequency oscillation signal generated from the magnetic oscillation element and the oscillation element.