Magnetic Memory Spin Filter Wiring for Writing Current Reduction
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Solution Overview
Problem
Current magnetic memory technologies face challenges in reducing the writing current required for magnetization reversal while preventing accidental magnetization reversal during reading, which affects recording density and memory functionality.
Innovation Solution
A magnetic memory structure with a spin filter integrated between writing and common wiring for magnetoresistance effect elements, allowing spin-polarized current injection only during writing and preventing it during reading, along with a specific wiring configuration to separate writing and reading currents and prevent short-circuiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If spin injection writing method is used to reduce writing current, then magnetization reversal efficiency is improved, but heat generation and breakdown risk increase due to high resistance
Solution Approach 1:
A spin filter layer is introduced as an intermediary component between the writing electrode and the magnetoresistance effect element. This spin filter selectively transmits spin-polarized electrons while blocking non-polarized electrons, enabling efficient spin injection with reduced current requirements and minimized heat generation.
Solution Approach 2:
The patent modifies the electrical and magnetic parameters of the writing electrode by adding the spin filter layer, which changes the spin polarization of the injected electrons. This parameter change allows for lower writing currents while maintaining effective magnetization reversal.
2Reliability
If reading current is minimized to prevent accidental magnetization reversal, then writing stability is improved, but reading function is compromised
Solution Approach 1:
The patent segments the electrode functions by creating separate reading and writing electrodes with distinct configurations. The writing electrode includes a spin filter for spin-polarized injection, while the reading electrode provides non-polarized current, allowing independent optimization of reading and writing operations.
Solution Approach 2:
Different regions of the device have different electrical properties: the writing path includes the spin filter layer for spin polarization, while the reading path does not. This local quality differentiation enables the reading current to be sufficiently high for reliable detection without causing accidental writing.
3Measurement precision
If TMR element resistance is high to maintain signal strength, then reading sensitivity is improved, but writing current increases causing heat and breakdown
Solution Approach 1:
The spin filter layer acts as a mediator that decouples the relationship between TMR element resistance and writing current. By providing spin-polarized electron injection, the spin filter enables efficient writing even with high-resistance TMR elements, as the spin-polarized electrons can more effectively induce magnetization reversal.
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 reduces the writing current while ensuring stable reading operations, enhancing recording density without compromising memory functionality by minimizing the reading current and improving magnetization reversal efficiency.
Implementation Method 1
a writing current is supplied between the first wiring and the common wiring via the spin filter, spin-polarized current is injected into the magnetoresistance effect element
Implementation Method 2
a spin torque by a spin current works on magnetization of the second ferromagnet. This spin torque serves as a driving force to cause a magnetization motion.
Implementation Method 3
A normal TMR element has a ferromagnetic layer/nonmagnetic insulating layer/ferromagnetic layer, three-layer structure... When the direction of magnetization of these two ferromagnets is antiparallel, the value of electrical resistance in the thickness direction is larger than that when the direction of magnetization is parallel.
Implementation Method 4
As a structure of the pinned layer, an exchange coupling type for which an antiferromagnetic layer (FeMn, IrMn, PtMn, NiMn, or the like) is given to one ferromagnetic layer is often used.
Implementation Method 5
It has been described in the same document that the stack has been deposited by a sputtering method and electron beam evaporation.
Implementation Method 6
It has been described in the same document that the stack has been deposited by a sputtering method and electron beam evaporation.
Data Source
AI summary
A magnetoresistance effect element is also located between second wiring and common wiring. The magnetoresistance effect element is electrically connected to the second wiring without a spin filter. When a reading current is supplied between the second wiring for supplying a reading current and the common wiring, since this is not supplied via a spin filter, no spin polarized current is supplied into the magnetoresistance effect element, so that it becomes difficult to magnetization-reverse a magnetosensitive layer. Even in a structure where, in order to improve recording density, the magnetosensitive layer is reduced in area so as to lower a writing current, no magnetization reversal occurs due to a supply of the reading current, and information can be read out without making the reading current considerably small in comparison with the writing current.