Magnetic Memory Spin Filter Configuration for Low Writing Current
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Solution Overview
Problem
Conventional magnetic memory technologies face challenges in reducing the magnitude of the writing current while maintaining detectable reading currents, especially as element size decreases, leading to inefficiencies in data storage and retrieval.
Innovation Solution
The magnetic memory design incorporates a magnetoresistance effect element with a free layer, a pinned layer, and nonmagnetic layers positioned within current paths to function as spin filters, allowing for reduced writing currents without necessitating a corresponding decrease in reading currents, by ensuring symmetry conditions are met between ferromagnetic materials and nonmagnetic layers during writing and reading operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the element size is reduced to increase integration density, then the writing current magnitude can be lowered, but the reading current becomes smaller than the detection limit
Solution Approach 1:
The patent divides the single magnetoresistance effect element into two separate elements: a first element for writing operations and a second element for reading operations. Each element has its own free layer, pinned layer, and spin filter layer configuration. This segmentation allows independent optimization of writing and reading functions, enabling the use of smaller element sizes for writing while maintaining adequate reading current levels through the second element's configuration.
2Productivity
If a magnetic path is constructed using soft magnetic material to concentrate the magnetic field, then the writing efficiency can be improved, but large energy is necessary to drive the soft magnetic material
Solution Approach 1:
The patent replaces the mechanical magnetic path system (using soft magnetic materials and concentrated magnetic fields) with an electronic spin injection system. Instead of using physical magnetic paths that require large driving energies, the invention uses spin-polarized electrons injected through spin filter layers to directly transfer angular momentum to the free layer, achieving magnetization reversal through quantum mechanical spin transfer torque rather than classical magnetic field concentration.
3Power
If spin injection is used to change the magnetization direction, then a comparatively large current is generally necessary, but magnetization reversal can be caused by a comparatively small current under specific conditions
Solution Approach 1:
The patent changes the magnetic configuration parameters of the spin filter layer relative to the pinned layer. Specifically, the spin filter layer is configured with a magnetization direction that is perpendicular to that of the pinned layer, creating a specific relative magnetic orientation. This parameter change enables efficient spin injection at lower current densities by optimizing the spin polarization transfer efficiency from the spin filter to the free layer, thereby achieving reliable magnetization reversal at reduced writing currents.
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 approach allows for a lower writing current magnitude without compromising the detectability of reading currents, even at smaller element sizes, thereby enhancing data storage efficiency and integration density.
Implementation Method 1
the direction of magnetization of the free layer can be changed by the spin injection. When electrons spinning in reverse are injected into the inside of the magnetic material, the direction of magnetization inside the magnetic material reverses (spin injection magnetization reversal) according to the injected spin
Implementation Method 2
By applying a current, spin having a specific polarity of magnetization injected into the inside of the free layer 3 via a spin filter or by being reflected by the spin filter torques the direction of magnetization of the free layer 3
Implementation Method 3
reads the stored information by measuring the quantity of electrons transmitted through the free layer
Implementation Method 4
a magnetic path is constructed by using a soft magnetic material or the like, and a magnetic field is supplied in a concentrated manner to the storage element through the inside of the magnetic path
Implementation Method 5
the direction of magnetization of the free layer is changed by an inductive magnetic field generated by a current supplied into the electric wire
Data Source
AI summary
The direction of magnetization of a reading ferromagnetic material 5R forming a spin filter when reading is the same as that of a pinned layer 1. In this case, a torque that works on the spin of a free layer 3 due to a spin polarized current becomes “zero.” When the element size is made small so as to improve the integration degree of the magnetic memory, according to the scaling law, the writing current can be made small. In the present invention, the resistance to the spin injection magnetization reversal due to a reading current is high, so that the magnitude of the writing current can be lowered.