Electric Field Control of Magnetic Tunnel Junctions
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Solution Overview
Problem
Current magneto-electronic devices lack efficient electric field-controlled magnetism for resistance switching, with existing materials like multiferroics and diluted magnetic semiconductors facing limitations such as low Curie temperature and insufficient resistance switching induced by electric fields.
Innovation Solution
A magneto-electronic device with an electric-field-controllable magnetic tunnel junction comprising ferromagnetic layers and an insulating MgO layer, where the magnetic anisotropies of the layers are alignable, and a voltage applied to change coercivity or tunneling potential energy barrier to switch between states, enabling efficient resistance switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiferroic materials are used to achieve electric field controlled magnetism, then magnetic anisotropy can be modified by electric field, but the Curie temperature is very low and the materials are not utilized in spintronics devices
Solution Approach 1:
The patent changes the material system from multiferroics to metallic ferromagnetic FePt and FePd films, which have high Curie temperatures. The electric field control mechanism is maintained through interface engineering with electrolytes, achieving both high temperature stability and device applicability
Solution Approach 2:
The patent creates a composite structure combining metallic ferromagnetic layers (FePt/FePd) with electrolyte interfaces. This composite approach enables electric field controlled magnetism in materials that inherently possess high Curie temperatures and are compatible with spintronics applications
2Temperature
If diluted magnetic semiconductors are used to achieve electric field controlled magnetism, then carrier density can be modified by gate voltage, but the Curie temperature is very low
Solution Approach 1:
The patent transitions from diluted magnetic semiconductors to metallic ferromagnetic systems where magnetic properties are controlled not by carrier density modulation but by electric field induced interfacial effects, thereby achieving high Curie temperature while maintaining electric field control
3Use of energy by moving object
If spin transfer torque effect is used to manipulate magnetization, then magnetization can be switched, but energy consumption is high compared to voltage-controlled methods
Solution Approach 1:
The patent replaces the spin transfer torque mechanism (which requires high current densities) with an electric field controlled mechanism acting through the electrolyte-film interface. This substitution reduces energy consumption by utilizing voltage control instead of high current spin-polarized transport
Solution Approach 2:
The patent introduces an electrolyte layer as an intermediary between the electric field source and the ferromagnetic film. This intermediary enables efficient coupling of electric field to the magnetic system, achieving low-energy magnetization control through interfacial effects rather than direct spin transfer
4Ease of operation
If electric field is applied to modify magnetic anisotropy in 3d transition ferromagnets, then magnetization reversal can be induced, but resistance switching has not been realized yet
Solution Approach 1:
The patent merges electric field controlled magnetization reversal with resistance switching functionality by combining the FePt/FePd magnetic tunnel junction structure with electrolyte gating. This integration achieves both magnetization control and resistive state switching, enabling memory and logic applications
Solution Approach 2:
The patent creates a composite magnetic tunnel junction structure with ferromagnetic layers, tunnel barrier, and electrolyte gate. This composite design simultaneously provides magnetization reversal control and resistance switching, fulfilling both functionalities in a single device architecture
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
The device achieves reversible resistance switching with reduced energy consumption by altering magnetic anisotropy and coercivity using electric fields, demonstrating improved energy efficiency and control over magnetization states.
Implementation Method 1
the essential feature of resistance switching induced by an electric field has not been realized yet
Implementation Method 2
The first and second ferromagnetic layers have respective first and second magnetic anisotropies that are alignable substantially parallel to each other in a first state and substantially antiparallel in a second state
Implementation Method 3
Magnetic tunnel junctions (MTJs), particularly MgO-MTJs with large tunnel magnetoresistance (TMR)
Implementation Method 4
A current of tunneling electrons through the insulating layer is greater in the first state than the second state
Implementation Method 5
a voltage applied between the first and second electrodes causes a change in at least one of a magnetic anisotropy energy, coercivity or domain wall velocity of at least one of the first and second ferromagnetic layers or a tunneling potential energy barrier through the insulating layer
Data Source
AI summary
A magneto-electronic device includes a first electrode, a second electrode spaced apart from the first electrode, and an electric-field-controllable magnetic tunnel junction arranged between the first electrode and the second electrode. The electric-field-controllable magnetic tunnel junction includes a first ferromagnetic layer, an insulating layer formed on the first ferromagnetic layer, and a second ferromagnetic layer formed on the insulating layer. The first and second ferromagnetic layers have respective first and second magnetic anisotropies that are alignable substantially parallel to each other in a first state and substantially antiparallel in a second state of the electric-field-controllable magnetic tunnel junction.