Magneto-Optical Device for Ultrafast MRAM Switching
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Solution Overview
Problem
Conventional magneto-resistive random-access memory (MRAM) technologies face challenges with high energy consumption, limited write selectivity, thermal stability, and slow operational speeds, particularly due to the requirements of large write currents and the scaling limitations that lead to overlapping magnetic fields and reduced reliability in smaller cell sizes.
Innovation Solution
An integrated magneto-optical device combining a magnetic unit with a femtosecond laser pulse to switch the magnetization in MRAM cells, utilizing a magnetic unit with two layers and an intermediate tunneling layer, where the laser pulse induces quenching of magnetization within 200-500 fs, significantly faster than electrical current pulses, and is electrically controlled with bias, enabling ultrafast and low-power data storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electrical current pulses are used to switch magnetization in MRAM cells, then the magnetization can be switched, but the switching speed is slow and energy consumption is high
Solution Approach 1:
The patent replaces the conventional electrical current-based magnetization switching mechanism with an optically-driven mechanism. A femtosecond laser pulse is used to induce ultrafast demagnetization in the magnetic layer, achieving switching speeds of 200-500 fs. This optical substitution eliminates the need for large write currents, thereby reducing energy consumption while dramatically increasing switching speed.
Solution Approach 2:
The patent changes the temporal parameter of the switching stimulus from nanosecond-scale electrical pulses to femtosecond-scale optical pulses. This parameter change in pulse duration enables ultrafast magnetization switching while reducing the total energy delivered to the magnetic cell, resolving the contradiction between speed and energy consumption.
2Ease of operation
If large write currents are used to switch magnetization, then magnetization switching can be achieved, but thermal stability deteriorates due to heating
Solution Approach 1:
The patent substitutes electrical current actuation with optical pulse actuation. The femtosecond laser pulse delivers energy so rapidly that it induces demagnetization before significant thermal diffusion can occur. This eliminates the thermal heating problem associated with large write currents while maintaining effective magnetization switching capability.
Solution Approach 2:
The patent employs ultrafast periodic optical pulsing to switch magnetization. The femtosecond duration of each pulse ensures that energy deposition is completed far faster than thermal relaxation times, allowing magnetization switching without thermal instability. The periodic nature of laser pulsing enables precise control over switching timing and temperature management.
3Area of stationary object
If cell size is reduced to increase memory density, then storage capacity increases, but magnetic fields overlap between adjacent cells reducing reliability
Solution Approach 1:
The patent employs localized optical addressing where each memory cell can be selectively targeted by the femtosecond laser pulse through precise spatial control. The optical focus can be confined to individual cells or specific regions, ensuring that magnetization switching occurs only in the intended cell without affecting adjacent cells. This local quality control maintains reliability even as cell sizes decrease and spacing becomes tighter.
Solution Approach 2:
The patent transitions from electrical field-based switching (which spreads laterally through conductive paths) to optical field-based switching (which can be focused in three-dimensional space). The laser pulse can be focused to a diffraction-limited spot, providing precise spatial selectivity in the vertical and lateral dimensions simultaneously, thereby preventing cross-cell interference even at high densities.
4Productivity
If conventional MRAM writing methods are used, then data can be written, but write selectivity is limited affecting the ability to write to specific cells
Solution Approach 1:
The patent implements optical addressing schemes where the laser beam can be spatially modulated or scanned to selectively address individual memory cells or groups of cells. By segmenting the optical addressing space, precise write selectivity is achieved - only the targeted cell receives sufficient optical energy for magnetization switching, while adjacent cells remain unaffected. This enables independent control of each cell for selective writing operations.
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 results in ultra-low power consumption, thermal stability, and extremely high operational speeds, exceeding prior art by several orders of magnitude, while allowing for faster control and manipulation of magnetization, integrating ultrafast laser pulses with MRAM technology to enhance scalability and cyclability.
Implementation Method 1
The second magnetic layer has a low Curie temperature and is switchable by heating above the Curie temperature
Implementation Method 2
the laser pulse induces quenching of magnetization within 200-500 fs
Implementation Method 3
A particular cell is selected by powering the associated transistor. The transistor switches a current from a supply line through the cell to ground. Thereby a magnetic tunnel effect is exploited.
Implementation Method 4
An integrated magneto-optical device combining a magnetic unit with a femtosecond laser pulse to switch the magnetization in MRAM cells
Data Source
Figure 1a~2b
Figure 3a~3b
AI summary
The present invention is in the field of a magneto optical device comprising a magnetic unit and an optical unit, an electronic device comprising the magneto-optic device, a method of energy saving using the magneto- optical device, an array comprising the magneto-optical devices, and a method of changing magnetic orientation.