VCMA MRAM Writing with Opposite Voltage Directions
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Solution Overview
Problem
Existing MRAM technologies require precise control of short pulse widths and initial reading to reverse magnetization directions, leading to extended write times and complex control circuits.
Innovation Solution
A memory device and system utilizing voltage-controlled magnetic anisotropy (VCMA) elements with opposite voltage directions for writing, eliminating the need for precise pulse width control and initial reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a unipolar pulse voltage is applied to reverse magnetization direction in VC-MRAM, then writing speed is improved, but pulse width control precision deteriorates requiring complex control circuits
Solution Approach 1:
The patent applies bipolar pulse voltages (with opposite polarities) instead of unipolar pulse voltages to control magnetization reversal. By inverting the voltage polarity direction, the system achieves reliable magnetization switching without requiring precise short pulse width control, thereby maintaining high writing speed while eliminating the need for complex control circuits
Solution Approach 2:
The patent changes the voltage parameter from unipolar to bipolar configuration. By applying voltages with opposite polarities during write operations, the system exploits the VCMA effect more effectively to achieve deterministic magnetization reversal at longer pulse widths, eliminating the trade-off between speed and control precision
2Reliability
If initial reading is performed before writing in VC-MRAM, then writing reliability is improved, but write time is extended
Solution Approach 1:
The patent eliminates the preliminary initial reading step by using bipolar pulse voltages that provide deterministic magnetization reversal. The opposite polarity voltages ensure reliable switching without needing to verify the initial state, thereby maintaining writing reliability while removing the time penalty associated with initial reading 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
Enables high-speed writing without complex circuits and reduced write times by using opposite voltage directions for resistance state transitions.
Implementation Method 1
the magnetoresistive element is a voltage-controlled magnetic anisotropy (VCMA) effect magnetoresistive element, and the write circuit controls the magnetoresistive element such that a first voltage for writing in a high resistance state and a second voltage for writing in a low resistance state have opposite directions
Implementation Method 2
A magnitude of the tunnel current depends on a relative angle of magnetization of the two magnetic layers. The above phenomenon is called a tunnel magneto resistance (TMR) effect
Implementation Method 3
a method of directly energizing a current to the MTJ element and utilizing a spin transfer torque (STT) effect
Data Source
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AI summary
Provided is a memory device including: a magnetoresistive element connected between a first control line and a second control line, a write circuit that controls writing to the magnetoresistive element, and a read circuit that controls reading from the magnetoresistive element. The magnetoresistive element is a voltage-controlled magnetic anisotropy (VCMA) effect magnetoresistive element, and the write circuit controls the magnetoresistive element such that a first voltage for writing in a high resistance state and a second voltage for writing in a low resistance state have opposite directions.