Spin Torque Oscillator Magnetic Recording Head
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Solution Overview
Problem
High-density magnetic recording is hindered by thermal fluctuations and the inefficiency of applying high-frequency magnetic fields, particularly in perpendicular magnetic recording, where existing techniques struggle to maintain coercivity and magnetic anisotropy energy.
Innovation Solution
A magnetic recording head incorporating a spin torque oscillator with a laminated structure, including a first magnetic layer, a second magnetic layer, and an intermediate layer, along with electrodes, generates a high-frequency magnetic field by passing current through the laminated body, which is designed to protrude beyond the main magnetic pole, allowing for localized resonance and reduced coercivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coil is used to generate a high-frequency magnetic field, then magnetic recording on high coercivity media is enabled, but efficient application of the high-frequency magnetic field during high-density recording becomes difficult
Solution Approach 1:
The spin torque oscillator is divided into multiple magnetic layers (first magnetic layer, second magnetic layer, intermediate layer) that can be independently optimized. This segmentation allows each layer to contribute specifically to generating the high-frequency magnetic field while maintaining stability, resolving the contradiction between reliable magnetic recording and efficient high-density recording application
Solution Approach 2:
The spin torque oscillator structure provides localized high-frequency magnetic field generation at the recording head-medium interface. By concentrating the high-frequency field application precisely where needed (at the protruding portion beyond the main magnetic pole), the system achieves both stable magnetic recording and efficient high-density recording without the diffusion problems associated with coil-based approaches
2Quantity of substance
If recording density is increased to exceed thermal fluctuations, then higher recording capacity is achieved, but thermal fluctuations manifest again at ultra-high densities
Solution Approach 1:
The spin torque oscillator generates a periodic high-frequency magnetic field that resonates with the magnetic recording medium at ultra-high densities. This periodic action temporarily reduces coercivity during the recording process, enabling stable magnetization even when thermal fluctuations would normally prevent reliable recording at such high densities
Solution Approach 2:
The system dynamically changes the magnetic field parameters by applying a high-frequency component that modulates the effective coercivity. This parameter change allows the recording medium to be written at ultra-high densities where static high coercivity would normally prevent stable recording due to thermal fluctuations
3Quantity of substance
If perpendicular magnetic recording is used to achieve high recording density, then recording capacity increases, but maintaining coercivity and magnetic anisotropy energy becomes difficult
Solution Approach 1:
The spin torque oscillator applies a preliminary high-frequency magnetic field to the recording medium before the main recording field is applied. This preliminary action resonates with the magnetic moments and temporarily reduces the effective coercivity, making it easier to write perpendicular magnetic recording at high densities without permanently compromising the medium's coercivity and magnetic anisotropy energy
Solution Approach 2:
The high-frequency magnetic field from the spin torque oscillator creates a form of magnetic vibration or resonance in the recording medium. This vibration temporarily disrupts the magnetic anisotropy, reducing the energy barrier for magnetization reversal and enabling perpendicular recording at high densities while preserving the medium's inherent coercivity and stability
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
This configuration enables efficient high-density magnetic recording by maintaining magnetization stability and preventing thermal fluctuations, allowing for higher recording densities and reliability in perpendicular magnetic recording.
Implementation Method 1
When a DC current is passed through the spin torque oscillator via the electrode, the spin torque generated by the spin injection layer produces ferromagnetic resonance in the magnetization of the magnetic layer
Implementation Method 2
the spin torque generated by the spin injection layer produces ferromagnetic resonance in the magnetization of the magnetic layer. Consequently, a high-frequency magnetic field is generated from the spin torque oscillator
Implementation Method 3
a high-frequency magnetic field near the resonance frequency of the magnetic recording medium, which is sufficiently higher than the recording signal frequency, is locally applied. This produces resonance in the magnetic recording medium, which decreases the coercivity (Hc) of the magnetic recording medium
Data Source
AI summary
A magnetic recording head includes: a main magnetic pole; a laminated body; and a pair of electrodes operable to pass a current through the laminated body. The laminated body includes a first magnetic layer, a second magnetic layer, and an intermediate layer provided between the first magnetic layer and the second magnetic layer. A lamination direction of the laminated body is substantially parallel to a medium moving direction. In a first direction parallel to an air bearing surface and perpendicular to the lamination direction, the laminated body has a protruding portion that protrudes beyond an end of a surface of the main magnetic pole facing the laminated body.