Carrier-Controlled Magnetic Memory for Ultra-Low Power Writing
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Solution Overview
Problem
As ferromagnetic materials are miniaturized, the magnetic field required for magnetization reversal increases, leading to high power consumption in nonvolatile magnetic memory, and reducing the writing current results in difficulties with reading output voltage, limiting large-scale integration and power efficiency.
Innovation Solution
The method involves controlling the direction of magnetization in a magnetic material by altering its anisotropy through carrier concentration changes, achieved by applying an electric field, eliminating the need for magnetic fields and spin currents, using a carrier-induced ferromagnetic material with a field effect transistor structure to rotate or reverse magnetization with ultra-low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic field required for magnetization reversal is increased to maintain stable magnetization in miniaturized ferromagnetic materials, then the reliability of data storage is improved, but the power consumption increases significantly
Solution Approach 1:
The patent replaces the conventional magnetic field-based magnetization reversal mechanism with a spin-polarized current injection mechanism. Instead of using external magnetic fields to reverse magnetization in miniaturized cells, the invention uses spin transfer torque from spin-polarized electrons to directly reverse the magnetization of the free layer, thereby reducing the power consumption associated with generating strong magnetic fields in small-scale devices
Solution Approach 2:
The patent changes the fundamental parameter for magnetization reversal from magnetic field strength to spin-polarized current density. By utilizing the spin angular momentum of electrons injected from the pinned layer through the tunnel barrier, the system achieves magnetization reversal at lower power consumption levels compared to conventional magnetic field methods, especially in miniaturized cell configurations
2Productivity
If the cell size is reduced to increase integration density, then the productivity of the memory device is improved, but the magnetic field required for magnetization reversal increases, leading to higher power consumption
Solution Approach 1:
The patent replaces the magnetic field-based reversal mechanism with spin transfer torque from spin-polarized current injection. This substitution enables effective magnetization reversal in miniaturized cells where conventional magnetic field methods would require prohibitively high power densities, thus enabling higher integration density without proportional increases in power consumption
Solution Approach 2:
The patent implements local spin polarization at the pinned layer interface with the tunnel barrier. The spin-polarized current is injected locally into the free layer, creating a localized magnetization reversal effect that is efficient for miniaturized cells. This local action mechanism allows each cell to be independently controlled with minimal power consumption regardless of cell size
3Use of energy by moving object
If the writing current is reduced to lower power consumption, then the energy efficiency is improved, but the output voltage for reading out becomes difficult to obtain
Solution Approach 1:
The patent employs dynamic magnetization switching using spin transfer torque, which enables reversible magnetization states to be achieved with low current densities. The dynamic nature of spin-polarized current injection allows for efficient writing operations that consume minimal power while maintaining distinct magnetization states that can be reliably read out through resistance changes in the tunnel magnetoresistive element
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 significantly reduces power consumption during writing operations, achieving ultra-low power usage in nonvolatile solid state magnetic memory, with power consumption estimated to be one millionth that of traditional methods, while maintaining data volatility without external magnetic fields or spin currents.
Implementation Method 1
applying an electric field is used as means for increasing or decreasing the carrier concentration
Implementation Method 2
making use of a magnetic material in which the magnetic anisotropy is changed by increasing or decreasing a carrier concentration
Implementation Method 3
there exists a method to reverse the magnetization by spin injection. This is a technique to reverse the magnetization in the free layer directly by injecting a spin polarized current from the pinned layer
Implementation Method 4
the magnetization direction in the free layer can be reversed by making use of a synthetic magnetic field which is generated by applying a current to the word and bit lines
Implementation Method 5
a bit '0' or '1' is determined depending on whether the magnetization directions in a top and bottom layer of a tunnel magnetoresistive element
Data Source
AI summary
A nonvolatile solid state magnetic memory with a ultra-low power consumption and a recording method thereof, the memory including a magnetic material having a magnetic anisotropy that can be changed by increasing or decreasing a carrier concentration, wherein a direction of an easy axis of magnetization, in which the magnetization is oriented easily, is controlled by increasing or decreasing the carrier concentration. The nonvolatile solid state magnetic memory including a recording layer of a magnetic material, and a recording method thereof, in which a carrier (electron or hole) concentration in the recording layer is increased and/or decreased, whereby the magnetization is rotated or reversed and the recording operation is performed.