Spin Torque Oscillator Asymmetric Stack for Stable RF Field
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Solution Overview
Problem
The challenge in achieving high-density magnetic recording is hindered by thermal fluctuations and the difficulty in efficiently applying a radio frequency magnetic field using spin torque oscillators, which are affected by the magnetic field from the main magnetic pole, leading to variations in oscillation frequency and magnetic field intensity.
Innovation Solution
A magnetic recording head design that includes a spin torque oscillator with a stacked structure of an oscillation layer, an intermediate layer, and a spin injection layer, where the spin injection layer has a larger film surface than the oscillation layer, and is positioned closer to the shield, allowing for efficient superposition of radio frequency and recording magnetic fields, and maintaining constant oscillation frequency and magnetic field intensity regardless of the recording magnetic field direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a coil is used to generate a radio frequency magnetic field, then a radio frequency magnetic field can be applied to the medium, but it is difficult to efficiently apply the radio frequency magnetic field to the medium
Solution Approach 1:
The patent replaces the conventional coil-based electromagnetic induction system with a spin torque oscillator that utilizes spin-polarized electron current to generate microwave-frequency magnetic fields. This substitution of the field generation mechanism enables more efficient and localized radio frequency magnetic field application to the magnetic recording medium.
Solution Approach 2:
The patent changes the operating parameters by using a DC current through the spin torque oscillator to generate a radio frequency magnetic field at microwave frequencies (e.g., 10 GHz), which is sufficiently higher than the recording signal frequency. This parameter change enables resonance in the magnetic recording medium and decreases the coercivity of the medium, facilitating efficient magnetic recording.
2Productivity
If the spin torque oscillator is brought close to the main magnetic pole, then the radio frequency magnetic field and recording magnetic field can be efficiently superposed, but the oscillation frequency and magnetic field intensity vary with the direction of the writing magnetic field
Solution Approach 1:
The patent introduces an asymmetric stacked structure where the spin injection layer has a larger film surface area than the oscillation layer and is positioned closer to the shield. This asymmetric configuration creates a magnetic field distribution that compensates for the variations caused by the main magnetic pole, maintaining stable oscillation frequency and magnetic field intensity regardless of the writing magnetic field direction.
Solution Approach 2:
The intermediate layer in the stacked structure acts as a mediator between the oscillation layer and the spin injection layer. This intermediate structure helps isolate and stabilize the oscillation characteristics from the external magnetic field variations, enabling consistent radio frequency magnetic field generation despite changes in writing magnetic field direction.
3Productivity
If high-density magnetic recording is performed, then recording density increases, but thermal fluctuations become manifest again
Solution Approach 1:
The patent employs periodic radio frequency magnetic field application through the spin torque oscillator to induce resonance in the magnetic recording medium at microwave frequencies. This periodic action temporarily reduces the coercivity of the medium during the recording process, enabling high-density recording while overcoming thermal fluctuations that would otherwise prevent stable magnetization at such high densities.
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 stabilizes the operation of the spin torque oscillator, reduces the inversion time of the spin injection layer, and enhances the efficiency of magnetic recording by ensuring consistent oscillation and magnetic field application, thereby overcoming thermal fluctuations and achieving high-density recording.
Implementation Method 1
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
Implementation Method 3
a radio frequency magnetic field near the resonance frequency of the magnetic recording medium... is locally applied to the medium. This produces resonance in the medium, which decreases the coercivity (Hc) of the portion of the medium subjected to the radio frequency magnetic field
Implementation Method 4
a magnetic field applied from a main magnetic pole
Data Source
AI summary
According to one embodiment, a magnetic recording head includes a main magnetic pole, a shield, and a stacked structure body. The shield is provided to oppose the main magnetic pole. The stacked structure body is provided between the main magnetic pole and the shield. The stacked structure body includes a first magnetic layer, a second magnetic layer, and an intermediate layer. The first magnetic layer has coercivity lower than a magnetic field applied from the main magnetic pole. A size of a film surface of the second magnetic layer is larger than a size of a film surface of the first magnetic layer. The intermediate layer is provided between the first magnetic layer and the second magnetic layer and is made of a nonmagnetic material. A current is configured to pass between the first magnetic layer and the second magnetic layer.