Hybrid Spin Torque Oscillator Geometry for MAMR Frequency Control
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Solution Overview
Problem
Conventional spin torque oscillators in perpendicular magnetic recording have insufficient control over frequency and write field optimization, limiting the reduction of magnetic grain size for increased aerial density, as they either lack sufficient frequency sensitivity or have a narrow lapping range for acceptable microwave field strength.
Innovation Solution
A spin torque oscillator with a substantially cylindrical member and a non-cylindrical member extending towards the air bearing surface, allowing for better frequency sensitivity and a wider lapping range, thereby optimizing microwave frequency and write field for microwave assisted magnetic recording.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional rectangular prism shaped STO is used, then the structure is simple to manufacture, but the frequency sensitivity with applied current is insufficient and the lapping range is narrow
Solution Approach 1:
The STO is divided into two distinct geometric segments: a substantially cylindrical member and a non-cylindrical member extending from it. This segmentation allows each part to contribute differently to the overall performance - the cylindrical portion provides frequency sensitivity while the non-cylindrical portion enables broader lapping range, resolving the contradiction between frequency control and manufacturing simplicity
Solution Approach 2:
The invention transitions from a conventional rectangular prism geometry to a hybrid geometry combining cylindrical and non-cylindrical elements. This dimensional change in the STO structure enables superior frequency sensitivity through the cylindrical symmetry while the extended non-cylindrical portion provides enhanced lapping range, achieving both performance goals simultaneously
2Measurement precision
If a cylindrical shaped STO is used, then the frequency sensitivity with applied current is improved, but the stripe height lapping range becomes very narrow
Solution Approach 1:
The invention merges the advantageous properties of cylindrical geometry (frequency sensitivity) with those of extended non-cylindrical geometry (lapping range). The hybrid structure combines these two geometric forms into a single STO device, allowing it to achieve both high frequency sensitivity and broad lapping range that neither geometry could provide alone
Solution Approach 2:
The non-cylindrical member extending from the cylindrical member creates a dynamic geometric profile that can be optimized for different lapping conditions. This extended portion provides the additional stripe height lapping range needed to accommodate varying microwave field strength requirements while the cylindrical base maintains frequency sensitivity
3Quantity of substance
If the magnetic grain size is reduced to increase aerial density, then the aerial density increases, but the write field strength required to switch magnetic grains increases
Solution Approach 1:
The STO generates periodic microwave fields that resonate with the magnetic grains at specific frequencies. This periodic electromagnetic action reduces the critical write field strength needed to switch magnetization in small magnetic grains, enabling high aerial density recording without requiring proportionally higher write fields that would damage the medium or require larger head structures
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 design enhances frequency control and write field optimization, enabling higher frequencies and broader lapping ranges, which facilitates improved magnetic recording density and stability.
Implementation Method 1
When an electrical current is applied to the STO, the polarization layer generates a spin-polarized current. The spin-polarized current is used to excite magnetic oscillations in the field generating layer and thereby generate a microwave field useful for MAMR applications.
Implementation Method 2
The spin-polarized current is used to excite magnetic oscillations in the field generating layer and thereby generate a microwave field useful for MAMR applications.
Implementation Method 3
The microwave field may have a frequency close to the resonance frequency of the magnetic grains to facilitate the switching of the magnetization of the grains at lower write fields than would otherwise be possible without assisted recording.
Data Source
AI summary
A microwave assisted magnetic recording (MAMR) write head includes a write pole tip, a trailing shield, and a spin torque oscillator between the write pole tip and the trailing shield. The spin torque oscillator may have a substantially cylindrical member and a non-cylindrical member extending from the substantially cylindrical member toward an air bearing surface (ABS). The non-cylindrical member may have a substantially rectangular and/or flat surface facing the ABS. Alternatively, the spin torque oscillator may include a substantially cylindrical member with a rectangular and/or flat surface facing the ABS that is lapped into the substantially cylindrical member.