Spin-Torque Oscillator Seed Layer for Magnetic Recording Write Head
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Solution Overview
Problem
In perpendicular magnetic recording systems, the integration of a spin-torque oscillator (STO) into the write head leads to spin polarization of electrons from the ferromagnetic write pole, counteracting the spin transfer torque, which hinders the magnetization switching of magnetic grains, necessitating a solution to maintain recording density and thermal stability.
Innovation Solution
A nonmagnetic electrically-conducting multilayer seed layer is introduced between the write pole and the ferromagnetic free layer to remove spin polarization, ensuring proper crystallographic texture and electron transport properties, while a nonmagnetic spacer layer separates the free layer from the polarizer, allowing spin-polarized electrons to be created by the trailing shield, thus maintaining the spin transfer torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a spin-torque oscillator is integrated into the write head to assist magnetic recording, then recording density and thermal stability are improved, but spin polarization from the ferromagnetic write pole counteracts the spin transfer torque, hindering magnetization switching
Solution Approach 1:
A nonmagnetic electrically-conducting seed layer is introduced as an intermediary between the ferromagnetic write pole and the ferromagnetic free layer. This seed layer removes spin polarization from electrons passing through it, preventing the counteracting effect on spin transfer torque while maintaining electrical conductivity for STO operation.
Solution Approach 2:
The seed layer is positioned specifically between the write pole and free layer where spin polarization removal is needed, while other regions maintain their original magnetic properties. This localized modification allows spin polarization removal exactly where required without affecting overall STO functionality.
2Manufacturing precision
If the size of magnetic grains is reduced to increase recording density, then more bits can be stored, but the magnetocrystalline anisotropy must be increased to maintain thermal stability, creating a conflicted limitation
Solution Approach 1:
The patent replaces conventional mechanical/field-based writing with spin-torque-based writing. The STO generates spin-polarized electrons that exert spin transfer torque on the magnetic grains, enabling magnetization switching at lower fields and smaller grain sizes while maintaining thermal stability through the unique spin-based mechanism.
3Device complexity
If a conventional write head is used without spin-torque oscillator, then the structure is simpler, but the write field must exceed the coercivity of the magnetic recording layer, limiting recording density
Solution Approach 1:
The patent merges the conventional write head structure with a spin-torque oscillator integrated between the write pole and trailing shield. The STO combines ferromagnetic layers separated by a nonmagnetic spacer, with electrical circuitry connected to the write pole and trailing shield, creating a hybrid system that leverages both conventional and spin-based writing mechanisms.
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 multilayer seed layer effectively removes spin polarization from electrons from the write pole, enhancing the magnetization switching of magnetic grains, improving recording density and thermal stability without adversely affecting the STO's performance, allowing for efficient microwave-assisted magnetic recording.
Implementation Method 1
A nonmagnetic electrically-conducting multilayer seed layer is introduced between the write pole and the ferromagnetic free layer to remove spin polarization
Implementation Method 2
the free layer can have a DC field component that will assist writing by the conventional write head
Implementation Method 3
a nonmagnetic spacer layer separates the free layer from the polarizer, allowing spin-polarized electrons to be created by the trailing shield
Implementation Method 4
a high frequency oscillatory auxiliary magnetic field from a ferromagnetic free layer or field generation layer (FGL) in the STO is applied to the magnetic grains of the recording layer
Data Source
AI summary
A magnetic recording write head and system has a spin-torque oscillator (STO) located between the write head's write pole and trailing shield. The STO's ferromagnetic free layer is located near the write pole with a multilayer seed layer between the write pole and the free layer. The STO's nonmagnetic spacer layer is between the free layer and the STO's ferromagnetic polarizer. The polarizer may be the trailing shield of the write head, one or more separate polarizer layers, or combinations thereof. The STO electrical circuitry causes electron flow from the write pole to the trailing shield. The multilayer seed layer removes the spin polarization of electrons from the write pole, which enables electrons reflected from the polarizer layer to become spin polarized, which creates the spin transfer torque on the magnetization of the free layer. The multilayer seed layer includes a Mn or a Mn-alloy layer.