Magnetic Tunnel Junction Writing with Single-Pulse Heating and Switching
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Solution Overview
Problem
Conventional methods for programming magnetic logical unit (MLU) cells face challenges with high voltage differences that can irreversibly weaken or destroy the cells due to the need for synchronized heating and field currents, leading to potential cell damage in MLU arrays.
Innovation Solution
A method involving a programming current pulse with distinct intensity portions is used to heat and magnetically field MLU cells, where a first pulse portion heats the cells to a high threshold temperature to unpin the storage magnetization, and a second pulse portion, with lower intensity, induces the programming magnetic field before cooling to a low threshold temperature, eliminating the need for synchronized heating and field currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heating current and field current are applied separately and synchronized, then programming precision is improved, but device complexity and risk of cell damage increase due to high voltage differences
Solution Approach 1:
The patent combines the heating current and field current into a single programming current that flows through the magnetic tunnel junction. This single current simultaneously provides both the heating effect (to overcome the blocking temperature of the antiferromagnetic layer) and the magnetic field effect (to switch the storage layer magnetization), eliminating the need for separate current paths and synchronization circuitry.
Solution Approach 2:
The programming current serves multiple functions simultaneously: it heats the magnetic tunnel junction to unpin the storage layer magnetization, generates the magnetic field for switching, and provides the necessary current for the write operation. This multi-functionality reduces device complexity while maintaining programming precision.
2Temperature
If heating current passes through magnetic tunnel junction in series array, then heating effectiveness is improved, but voltage difference increases causing cell damage
Solution Approach 1:
The patent changes the temporal parameters of the programming current, using a pulsed current waveform with controlled duration and amplitude. The pulse is designed to provide sufficient heating power while limiting the total energy delivery and peak voltage stress on the magnetic tunnel junction, preventing irreversible damage to the cell.
Solution Approach 2:
The programming operation uses a periodic pulsed current approach rather than continuous current. The pulse duration is carefully controlled to achieve the necessary heating effect (raising temperature above the blocking temperature temporarily) while minimizing the exposure time to high voltage conditions that could damage the cell structure.
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 risk of cell damage and enhances the robustness of MLU cells and arrays by using a single field current for both heating and programming, eliminating the need for precise synchronization and minimizing voltage-induced stress.
Implementation Method 1
passing the programming current pulse in the field line for heating the magnetic tunnel junction of each of said plurality of MLU cells at the high threshold temperature such as to unpin the ferromagnetic storage magnetization
Implementation Method 2
The programming current pulse is further adapted for generating a programming magnetic field adapted for switching the storage magnetization of each of said plurality of MLU cells in a programmed direction
Implementation Method 3
cool the magnetic tunnel junction at the low threshold temperature
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3c
AI summary
The present disclosure concerns a method for programming a magnetic device (100) comprising a plurality of MLU cells (1), where each MLU cell (1) includes a storage magnetic layer (23) having a storage magnetization (231) that is pinned at a low threshold temperature (TL) and freely orientable at a high threshold temperature (TH); and a programming line (4) physically separated from each of said plurality of MLU cells (1) and configured for passing a programming current pulse (41) for programming any one of said plurality of MLU cells (1); the method comprising: passing the programming current (41) in the field line (4) for heating the magnetic tunnel junction (2) of each of said plurality of MLU cells (1) at the high threshold temperature (TH) such as to unpin the second magnetization (231); wherein the programming current (41) is further adapted for generating a programming magnetic field (42) adapted for switching the storage magnetization (231) of each of said plurality of MLU cells (1) in a programmed direction.