MRAM Cell Voltage-Controlled Magnetization Switching
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Solution Overview
Problem
Current Magnetoresistive Random Access Memory (MRAM) technologies face challenges in scalable and energy-efficient 'write' operations due to the need for large magnetic fields and currents, leading to increased probability of false writes and limited scalability.
Innovation Solution
A memory cell design incorporating a magnetic element with a non-ferromagnetic spacer layer and a resistance switching material whose carrier density is altered by electrical voltage, allowing for magnetization switching between states without magnetic fields or high currents, utilizing transition metal oxides for resistance switching and oxygen vacancies for ion concentration changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large magnetic fields and currents are used for write operations in conventional MRAM, then magnetization switching is achieved, but energy consumption increases and false writes occur
Solution Approach 1:
The patent replaces the conventional magnetic field-based switching mechanism with an electric field-based mechanism. A control electrode is positioned adjacent to the ferromagnetic layer, and applying a voltage to this electrode generates an electric field that directly modulates the magnetization switching process. This substitution of magnetic field control with electric field control reduces energy consumption and improves write operation accuracy by enabling precise, localized control without requiring large currents through the entire memory cell.
2Productivity
If conventional write operations are used, then magnetization switching is achieved, but scalability is limited due to large current requirements
Solution Approach 1:
The patent replaces the conventional magnetic field-based switching mechanism with an electric field-based mechanism. A control electrode is positioned adjacent to the ferromagnetic layer, and applying a voltage to this electrode generates an electric field that directly modulates the magnetization switching process. This substitution of magnetic field control with electric field control reduces energy consumption and improves write operation accuracy by enabling precise, localized control without requiring large currents through the entire memory cell.
Solution Approach 2:
The control electrode provides localized control over the magnetization switching process. By positioning the control electrode adjacent to the ferromagnetic layer and applying voltage only to this specific region, the electric field is concentrated where needed. This localized control enables independent addressing of individual memory cells or small groups of cells, improving scalability by allowing denser memory arrays without interference between adjacent cells.
3Reliability
If magnetic fields are applied for write operations, then magnetization switching occurs, but the probability of false writes in neighboring cells increases
Solution Approach 1:
The patent replaces the conventional magnetic field-based switching mechanism with an electric field-based mechanism. A control electrode is positioned adjacent to the ferromagnetic layer, and applying a voltage to this electrode generates an electric field that directly modulates the magnetization switching process. This substitution of magnetic field control with electric field control reduces energy consumption and improves write operation accuracy by enabling precise, localized control without requiring large currents through the entire memory cell.
Solution Approach 2:
The control electrode provides localized control over the magnetization switching process. By positioning the control electrode adjacent to the ferromagnetic layer and applying voltage only to this specific region, the electric field is concentrated where needed. This localized control enables independent addressing of individual memory cells or small groups of cells, improving scalability by allowing denser memory arrays without interference between adjacent cells.
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 enables efficient, low-energy 'write' operations, improving scalability and reducing energy consumption, making MRAM technology more suitable for dense and fast applications like computer main memory or CPU cache.
Implementation Method 1
a resistance switching material, a carrier density of which may be altered by causing an ion concentration to alter by means of an applied electrical voltage signal
Implementation Method 2
resistance switching material
Implementation Method 3
magnetoresistive element, for example an anisotropic magnetoresistive (AMR) element, a metallic multilayer element exhibiting the giant magnetomagentoresistance (GMR) effect, or a multilayer element with a magnetic tunnel junction (MTJ) thus exhibiting the Tunneling Magnetoresistance (TMR)
Implementation Method 4
An effective exchange coupling between the second and the third ferromagnetic layer is subject to the carrier density state
Data Source
Figure 1~3
Figure 4a~4b
Figure 4c~6
AI summary
A memory cell according to the invention comprises a magnetic element that includes a first and a second ferromagnetic layer (11, 12), the relative orientation of the magnetizations of which defines a data bit, the first and second ferromagnetic layers being separated by a non-ferromagnetic, preferably electrically insulating spacer layer (13). The data bit can be read out, as is known in the art of magnetic RAM, by measuring the electrical resistance across the magnetic element, preferably perpendicular to a layer plane. In addition to the magnetic element, the memory cell comprises a further, third ferromagnetic layer (15), the magnetization direction of which is well-defined, and a resistance switching material (14), a carrier density of which may be altered by causing an ion concentration to alter by means of an applied electrical voltage signal. By this, the carrier density may be switched between a first and a second state, an effective exchange coupling between the second and the third ferromagnetic layer being influenced in a manner that an overall magnetic coupling between the magnetizations of the second and the third ferromagnetic layer changes directions, i.e. a the overall magnetic coupling favors different relative orientations of the magnetization directions of the second and third ferromagnetic layers.