Voltage-Controlled Magnetoresistive Memory Switching
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Solution Overview
Problem
Conventional magnetoresistive devices face challenges in reducing power consumption, particularly as device size decreases, due to the increased magnetic field required to switch the free layer, and existing methods like spin transfer switching require high current densities or external magnetic fields, limiting scalability and power efficiency.
Innovation Solution
A magnetoresistive device with a ferromagnetic layer structure featuring a quantum well structure and tunable exchange coupling, where an electric field pulse induces magnetization reversal by changing the magnetic anisotropy, allowing for reduced power consumption and scalable operation without external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the size of the cell decreases, then the scalability and integration density improve, but the magnetic field required to switch the free layer increases leading to higher power consumption
Solution Approach 1:
The patent replaces the conventional spin transfer switching mechanism (which requires high current density) with a voltage-controlled magnetic anisotropy switching mechanism. By applying voltage pulses to control the magnetic anisotropy energy rather than directly switching magnetization through spin torque, the invention achieves magnetization switching at significantly lower current densities, thereby resolving the power consumption issue that worsens with cell size reduction
Solution Approach 2:
The invention changes the magnetic anisotropy parameter (from perpendicular to in-plane or vice versa) by applying voltage pulses that modify the interfacial anisotropy energy. This parameter change enables the magnetic field required for switching to be dynamically controlled, allowing small cells to switch at lower fields when voltage is applied, thus resolving the contradiction between cell size and power consumption
2Device complexity
If spin transfer switching is used to avoid external magnetic fields, then the device complexity is reduced, but high current density is required which increases power consumption
Solution Approach 1:
The patent substitutes the spin transfer torque mechanism (current-driven) with a voltage-driven magnetic anisotropy control mechanism. Instead of using high current density to generate spin-polarized electrons that exert torque on the magnetization, the invention uses voltage pulses to modulate the magnetic anisotropy energy landscape, enabling switching at much lower current densities while maintaining the simple magnetic tunnel junction structure
Solution Approach 2:
The invention introduces dynamic control of magnetic anisotropy through voltage pulses, making the anisotropy parameter time-dependent. This dynamic modulation of the energy landscape allows the system to transition between stable magnetic states using minimal energy, resolving the contradiction between structural simplicity and power consumption by adding temporal control rather than structural complexity
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 enables efficient magnetization switching with lower current densities and reduced power consumption, enhancing scalability and operational efficiency by utilizing electric field pulses to control magnetic anisotropy and exchange coupling in the device.
Implementation Method 1
the quantum well structure configured to exhibit at least one quantised energy state, wherein exchange coupling between the first and second ferromagnetic layers is controllable through the at least one quantised energy state
Implementation Method 2
a first ferromagnetic layer exhibiting magnetic anisotropy in a first direction with a pinned magnetisation orientation, a second ferromagnetic layer exhibiting magnetic anisotropy in a second, different direction
Implementation Method 3
When spin polarised electrons are injected into the free layer, they interact with the free layer and transfer a portion of their spin angular momentum to the magnetic moment of the free layer
Implementation Method 4
The magnetoresistance of the element is relatively high if the magnetisations of the layers are arranged in anti-parallel (AP) and is relatively low if the magnetisations of the layers are arranged in parallel (P)
Data Source
Figure 1(a)~2(c)
Figure 3(a)~4
Figure 5(a)~6(b)
AI summary
A method of operating a magnetoresistive device is described. The device comprises a ferromagnetic region configured to exhibit magnetic anisotropy and to allow magnetisation thereof to be switched between at least first and second orientations and a gate capacitively coupled to the ferromagnetic region. The method comprises applying an electric field pulse to the ferromagnetic region so as to cause orientation of magnetic anisotropy to change for switching magnetisation between the first and second orientations.