Antiferromagnetically Coupled STO Device for MAMR Write Field Enhancement
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Solution Overview
Problem
Current spin torque (STO) devices fail to simultaneously achieve significant spin-torque-induced flux guiding layer (FGL) reversal and microwave assisted magnetic recording (MAMR) effects, leading to suboptimal write performance in hard disk drives due to high current density requirements and limited MAMR effect.
Innovation Solution
A STO device design featuring an antiferromagnetically coupled spin polarization (SP) layer configuration with a seed layer, non-magnetic spacers, and a flux guiding layer, where the SP layers oscillate to generate a radio frequency field, enabling both FGL reversal and MAMR effects at reduced current densities, thereby enhancing write field output and reducing the write field required for magnetic bit switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high current density is applied to achieve spin torque effect for FGL reversal, then write field output is enhanced, but current consumption increases and MAMR effect diminishes due to reduced oscillation cone angle
Solution Approach 1:
The spin polarization layer is divided into two separate layers (SP1 and SP2) that are antiferromagnetically coupled. This segmentation allows each layer to contribute independently to the spin torque effect on the FGL, enabling FGL reversal at lower current densities while maintaining sufficient oscillation amplitude for MAMR effect
Solution Approach 2:
The device uses a composite structure combining two ferromagnetic layers (SP1 and SP2) with antiferromagnetic coupling through a Ru layer. This composite configuration creates synergistic effects where the antiparallel magnetization arrangement enhances spin torque efficiency while preserving oscillation characteristics needed for MAMR
2Stability of the object's composition
If high current density is applied to achieve spin torque effect, then FGL reversal is achieved, but MAMR effect becomes insignificant due to smaller oscillation cone angle
Solution Approach 1:
The antiferromagnetically coupled SP layers are designed to dynamically oscillate in response to applied current, maintaining a substantial oscillation cone angle even at reduced current densities. This dynamic behavior enables simultaneous achievement of FGL reversal and MAMR effect
Solution Approach 2:
The device changes the magnetic configuration parameters by using antiparallel magnetization in the two SP layers coupled through antiferromagnetic interaction. This parameter change enables enhanced spin torque efficiency for FGL reversal while maintaining oscillation amplitude sufficient for MAMR effect at lower current 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
The proposed STO device design improves writability by achieving substantial FGL reversal and MAMR effects at lower current densities, enhancing write field output and reducing the write field needed for magnetic bit switching, thus addressing the limitations of prior art STO devices.
Implementation Method 1
Spin transfer torque devices (also known as STO devices) are based on a spin-transfer effect that arises from the spin dependent electron transport properties of ferromagnetic-spacer-ferromagnetic multilayers. When a spin-polarized current passes through a magnetic multilayer in a CPP (current perpendicular to plane) configuration, the spin angular moment of electrons incident on a ferromagnetic layer interacts with magnetic moments of the ferromagnetic layer near the interface between the ferromagnetic and non-magnetic spacer. Through this interaction, the electrons transfer a portion of their angular momentum to the ferromagnetic layer.
Implementation Method 2
MAMR uses a spin torque device to generate a high frequency field that reduces the coercive field of a medium bit thereby allowing the bit to be switched with a lower main pole field. the SP layers oscillate to generate a radio frequency field, enabling both FGL reversal and MAMR effects
Implementation Method 3
FGL magnetization flips to an opposite direction as a result of spin torque from adjacent spin polarization (SP) layers when a current (Ia) of sufficient density is applied thereby enhancing the main pole write field, and wherein first and second spin polarization (SP1 and SP2) layers in an antiferromagnetic (AF) coupling configuration oscillate to provide a MAMR effect
Data Source
AI summary
A spin torque transfer (STO) assisted magnetic recording structure is disclosed wherein a STO device has capability to generate a radio frequency (RF) field on a magnetic bit to lower the required write field during a write process. The STO device contains a field generation layer (FGL) with a magnetization that flips to a direction opposite to the write gap field when a current of sufficient current density is applied thereby increasing reluctance in the write gap and causing a larger write field output at the air bearing surface. A key feature is that a single spin polarization (SP) layer and an antiferromagnetically coupled SP layer comprised of SP1 and SP2 layers are formed on opposite sides of the FGL. SP1 magnetization is greater than SP2 magnetization. Additive torque from SP and SP2 layers on the FGL enables FGL flipping while SP1 and SP2 precessional states provide the RF field.