Voltage-Controlled Magnetic Device for Wide Temperature MRAM
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Solution Overview
Problem
Current magnetic random access memory (MRAM) devices face challenges in reducing power consumption, particularly during writing operations, due to high current densities that can lead to dielectric breakdown and limited operating temperature ranges, making it difficult to maintain low-power writing across a wide temperature range.
Innovation Solution
A voltage-controlled magnetic device with a multilayer stack that adjusts magnetic anisotropy using an electric field, allowing for switching between perpendicular and in-plane magnetization directions, thereby optimizing the effective anisotropy to remain close to a reorientation transition over a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If current magnetic random access memory devices use conventional writing methods with magnetic fields induced by current flow, then writing operations can be performed, but power consumption increases significantly with currents of the order of a few mA requiring several tens of pJ energy per write operation
Solution Approach 1:
The patent replaces the conventional magnetic field-based writing mechanism (mechanical/electromagnetic system) with an electric field-based mechanism. By applying voltage pulses to control the magnetic anisotropy energy and induce magnetization switching, the device eliminates the need for high current densities, reducing writing energy from tens of pJ to much lower levels while maintaining reliability.
Solution Approach 2:
The patent changes the fundamental parameter controlling magnetization switching from current density to electric field/voltage. By controlling the magnetic anisotropy energy through applied voltage, the system achieves magnetization reversal at significantly lower energy consumption, transforming the writing mechanism from a high-power electromagnetic process to a low-power electrostatic control process.
2Reliability
If magnetic tunnel junctions use high current densities for writing operations, then magnetization switching can be achieved, but dielectric breakdown occurs limiting the operating temperature range
Solution Approach 1:
The patent substitutes the high-current-density electromagnetic writing mechanism with an electric field-based control mechanism. By using voltage pulses to modulate magnetic anisotropy, the system avoids high current densities that cause dielectric breakdown, thereby extending the operating temperature range while maintaining low energy consumption for writing operations.
3Use of energy by moving object
If voltage-controlled magnetic devices use electric field to control magnetization, then power consumption is reduced, but maintaining low-power writing across a wide temperature range becomes challenging
Solution Approach 1:
The patent introduces dynamic control of magnetic anisotropy through applied voltage, allowing the device to adapt its magnetic properties in real-time. By controlling the electric field, the system can maintain optimal magnetization switching conditions across different temperatures, enabling low-power writing operations throughout a wide temperature range from cryogenic to elevated temperatures.
Solution Approach 2:
The patent utilizes voltage-controlled changes in magnetic anisotropy energy to adapt the device behavior across different temperature conditions. By adjusting the electric field parameter, the system compensates for temperature-induced variations in magnetic properties, maintaining effective low-power writing control across a broad temperature spectrum.
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 low-power writing in MRAM devices by effectively controlling magnetization orientation using an electric field, ensuring reliable operation across a broad temperature range while reducing energy consumption and enhancing device reliability.
Implementation Method 1
the application of a bias voltage Vmax allows modifying the surface anisotropy KSA of the magnetic layer 2, so as to switch the effective anisotropy Keff
Implementation Method 2
said magnetic layer having an anisotropy switching threshold such as the application of a bias voltage Vmax allows the switching of the effective anisotropy Keff from a direction perpendicular to the reference plane to a direction in the reference plane
Implementation Method 3
the writing is performed by applying a spin-polarized current across the magnetic tunnel junction so as to exert on the magnetization of the storage layer a torque capable of modifying it
Implementation Method 4
The resistance of the device typically varies by a factor of 2 to 3 depending on whether the magnetization of the two ferromagnetic layers is parallel or antiparallel, thus providing a numerical '0' or '1'
Implementation Method 5
The write energy is mainly associated with the dissipation by Joule effect in the magnetic tunnel junction and in the conductive wires connected to the electrodes of the magnetic tunnel junction
Data Source
Figure 1a~1f
Figure 2~3b
Figure 4~5
AI summary
The invention essentially relates to a voltage-controlled spintronic device comprising: - a magnetic layer having an effective anisotropy Keff; - a non-magnetic insulating layer; - a contact layer; said magnetic layer having an anisotropy switching threshold such that the application of a polarisation voltage Vmax allows switching of the effective anisotropy Keff from a direction perpendicular to the reference plane to a direction in the reference plane or vice versa, the magnetic layer comprising: - a first layer, with thickness tB, having a volume anisotropy KVB; - a second layer, with thickness tA, having a surface anisotropy KSA and a volume anisotropy KVA; the surface anisotropy KSA and the volume anisotropies KVA and KVB respecting, over a given operating temperature range, the following inequality: Min(KSA(V = 0), KSA(V = Vmax)) < -{KVBtB + KVAtA) < Max(KSA(V = 0), KSA(V = Vmax)) where KSA(V=0) is the surface anisotropy when no polarisation voltage is applied and KSA(V=Vmax) is the surface anisotropy when a polarisation voltage Vmax is applied.