CoB SOT Layer Structure for Negative Magnetostriction and Low Coercivity
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Solution Overview
Problem
Spin-orbit torque (SOT) devices face limitations in achieving negative magnetostriction, low coercivity, and high resistivity due to material melting, migration, and large grain sizes, which hinder their performance in magnetic recording and storage applications.
Innovation Solution
A cobalt-boron (CoB) layer is introduced between a seed layer and a cap layer in SOT devices, with a nano layer under the CoB layer to enhance polarization and magnetostrictive properties, and insertion layers above the CoB layer to control magnetostriction and resistivity, forming a ferromagnetic CoB layer that is substantially free from other materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional material configurations are used in SOT devices, then device structure is simpler, but negative magnetostriction, low coercivity, and high resistivity cannot be achieved simultaneously
Solution Approach 1:
The patent employs a composite layered structure consisting of CoB layer, nano layer, insertion layers, seed layer, and cap layer. Each layer contributes specific properties: the CoB layer provides ferromagnetism and negative magnetostriction, the nano layer enhances polarization, and the insertion layers control magnetostriction and resistivity. This composite approach enables simultaneous achievement of negative magnetostriction, low coercivity, and high resistivity that cannot be obtained with conventional single-material configurations.
Solution Approach 2:
Different regions of the device are assigned different material compositions and properties to optimize local functionality. The CoB layer is positioned specifically to provide negative magnetostriction, while nano layers are placed to enhance polarization in critical regions. This spatial differentiation of material properties allows each region to contribute optimally to the overall device performance.
2Reliability
If conventional material configurations are used, then manufacturing process is simpler, but material melting, migration, and large grain sizes occur
Solution Approach 1:
The patent utilizes controlled changes in material composition parameters, layer thicknesses, and stoichiometric ratios to prevent material degradation. By optimizing the composition of the CoB layer and the thickness of the nano and insertion layers, the device achieves stable magnetic properties while preventing material melting, migration, and excessive grain growth during fabrication and operation.
Solution Approach 2:
The multi-layer composite structure provides mutual protection against material degradation. The seed layer protects underlying layers during deposition, while the cap layer protects surface layers from oxidation and contamination. The insertion layers act as diffusion barriers preventing material migration between adjacent layers, thus improving overall material stability.
3Reliability
If CoB layer is introduced with nano layer and insertion layers, then negative magnetostriction and low coercivity are achieved, but device structure becomes more complex
Solution Approach 1:
The device is segmented into functionally distinct layers: the CoB layer specifically addresses coercivity and magnetostriction, the nano layer handles polarization enhancement, and the insertion layers manage resistivity control. This segmentation allows each component to be optimized independently for its specific function while contributing to the overall device performance.
Solution Approach 2:
The multi-layer structure serves multiple functions simultaneously: the CoB layer provides both ferromagnetism and negative magnetostriction, the nano layer enhances polarization while also serving as a structural template, and the insertion layers control both magnetostriction and resistivity. This multi-functionality reduces the need for additional specialized layers.
4Reliability
If CoB layer is used with strict material composition, then high resistivity is achieved, but material selection becomes more restricted
Solution Approach 1:
The patent achieves high resistivity by precisely controlling the composition parameters of the CoB layer, specifically the cobalt-to-boron ratio and the presence of minimal impurities. By adjusting these compositional parameters within specific ranges, the device achieves optimized resistivity while maintaining compatibility with standard fabrication processes and available materials.
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 CoB layer facilitates negative magnetostriction, low coercivity, and high resistivity, leading to improved recording performance, high signal-to-noise ratios, and reduced shunting in SOT devices, enhancing their magnetic recording and storage capabilities.
Implementation Method 1
The NL is under the CoB layer and has a polarization that is higher than the CoB layer which can increase the polarization of (e.g., polarize) the CoB free layer (FL) layer
Implementation Method 2
enhance negative magnetostrictive properties of the CoB layer
Implementation Method 3
The CoB layer is ferromagnetic
Implementation Method 4
facilitates negative magnetostriction
Implementation Method 5
insertion layers above the CoB layer such that the CoB layer is between the NL and the one or more insertion layers
Implementation Method 6
control magnetostriction and resistivity
Data Source
AI summary
Embodiments of the present disclosure relate to a cobalt-boron (CoB) layer for magnetic recording devices, memory devices, and storage devices. In one or more embodiments, the CoB layer is part of a spin-orbit torque (SOT) device. In one or more embodiments, the SOT device is part of an SOT based sensor, an SOT based writer, a memory device (such as a magnetoresistive random-access memory (MRAM) device), and/or a storage device (such as a hard disk drive (HDD) or a tape drive). In one embodiment, an SOT device includes a seed layer, and a cap layer spaced from the seed layer. The SOT device includes a spin-orbit torque (SOT) layer, and a nano layer (NL) between the seed layer and the cap layer. The SOT device includes a cobalt-boron (CoB) layer between the seed layer and the cap layer, and the CoB layer is ferromagnetic.