Magnetic Memory Read Circuit Stabilization
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Solution Overview
Problem
The existing read-system circuits for magnetic memory devices are not suited for the spin injection write method, leading to variations in read current that can cause data disturbance and require different peripheral circuits compared to the magnetic field write method.
Innovation Solution
A magnetic memory device design that includes a first magnetoresistive element switching between high and low resistance states based on write current direction, a second magnetoresistive element fixed to a specific resistance state depending on read current direction, and a control circuit ensuring equal read voltages for both elements, along with MOSFETs and operational amplifiers to manage these states and currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional read-system circuit is used with spin injection write method, then the circuit can perform basic read operations, but read current variations occur causing data disturbance
Solution Approach 1:
The patent creates a replica magnetoresistive element that copies the electrical characteristics of the actual memory element. This replica element is used to generate a reference signal that compensates for read current variations, thereby maintaining measurement precision and preventing data disturbance while preserving reliability
Solution Approach 2:
The patent implements a feedback mechanism where the read current is continuously monitored and compared against a reference value. The difference signal is fed back to adjust the read current in real-time, ensuring stable operation and preventing data disturbance caused by current variations
2Adaptability or versatility
If different peripheral circuits are designed for magnetic field write and spin injection write methods, then each method gets optimized circuit support, but device complexity increases
Solution Approach 1:
The patent designs a universal read-system circuit that can accommodate both magnetic field write and spin injection write methods. The circuit uses configurable components and control logic that can be adjusted based on the write method being used, eliminating the need for completely separate peripheral circuits while maintaining optimized performance for each method
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 configuration stabilizes the read current, reduces variations, and allows for a peripheral circuit optimized for the spin injection write method, preventing data disturbance and enabling efficient data reading.
Implementation Method 1
a so-called spin injection write method has been proposed... the current of electrons spin-polarized by the magnetic moment in the fixed layer of the magnetoresistive element is supplied to its free layer. Since the direction of magnetization in the free layer changes in accordance with the direction of this electron current
Implementation Method 2
The magnetoresistive element includes a free layer and fixed layer made of a magnetic material and a nonmagnetic layer sandwiched between them, and takes different resistance states in accordance with the direction of magnetization in the free layer
Data Source
AI summary
There is provided a magnetic memory device including a first magnetoresistive element which takes a high-resistance-state when receiving a write current in a first direction, takes a low-resistance-state having a resistance value lower than that in the high-resistance-state when receiving a write current in a second direction opposite to the first direction, and receives a read current in a read operation, a second magnetoresistive element which takes one of the high-resistance and low-resistance-states in accordance with a magnetization state thereof, is fixed to the low-resistance-state when a direction of the read current is the same as the first direction, and is fixed to the high-resistance-state when the direction of the read current is the same as the second direction, and a control circuit which is connected to the first and second elements, and makes a read voltage applied to the first element equal to that applied to the second element.