Ferromagnetic Multilayer Film with Interposed Layers for Exchange Coupling
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Solution Overview
Problem
The existing ferromagnetic multilayer films with a synthesized anti-ferromagnetic structure (SAF) face challenges in maintaining a strong antiferromagnetic exchange coupling magnetic field due to element diffusion at the interfaces during the manufacturing process, leading to weakened magnetization direction fixing and reduced magnetoresistive effect ratios.
Innovation Solution
A ferromagnetic multilayer film structure is designed with a first and second interposed layer between the ferromagnetic layers and a magnetic coupling layer, where the main element of the interposed layers matches or differs from the magnetic coupling layer, and their thicknesses are optimized to suppress element diffusion and maintain strong antiferromagnetic exchange coupling, using materials like Ru, Rh, or Ir for the magnetic coupling layer and Mo, W, Ti, Zr, Pd, Ag, Hf, Pt, or Au for the interposed layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If elements are diffused between the ferromagnetic layers and the magnetic coupling layer at the interface, then the interface becomes non-abrupt and manufacturing is easier, but the exchange coupling magnetic field strength decreases and magnetization direction fixing is weakened
Solution Approach 1:
A non-magnetic spacer layer is introduced as an intermediary between the ferromagnetic layer and the magnetic coupling layer. This spacer layer prevents direct diffusion of elements between the ferromagnetic layer and magnetic coupling layer, maintaining an abrupt interface while still allowing the exchange coupling magnetic field to effectively couple the magnetization directions. The spacer acts as a barrier that mediates the interaction between the two layers.
2Strength
If the interface between ferromagnetic layers and magnetic coupling layer is made abrupt, then the exchange coupling magnetic field strength is enhanced, but element diffusion is suppressed requiring more precise manufacturing control
Solution Approach 1:
The non-magnetic spacer layer serves as a mediator that creates a well-defined, abrupt interface between the ferromagnetic layer and magnetic coupling layer. By introducing this intermediate layer with controlled thickness, the manufacturing process can achieve precise interface control without requiring direct contact between the ferromagnetic and magnetic coupling layers, thus maintaining abrupt interfaces with standard manufacturing tolerances.
3Stability of the object's composition
If the magnetization direction fixing is strengthened using SAF structure, then the magnetization direction stability is improved, but the device complexity increases due to additional layers
Solution Approach 1:
The invention extracts and isolates the essential function of the SAF structure by introducing only a non-magnetic spacer layer between the ferromagnetic layer and magnetic coupling layer. This simplified approach maintains the magnetization direction stability provided by SAF structures while reducing device complexity by eliminating the need for multiple additional magnetic coupling layers and complex stacking sequences.
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 enhances the antiferromagnetic exchange coupling magnetic field strength, preventing magnetization direction changes under external fields and spin torque, thereby improving the magnetoresistive effect ratio and signal symmetry.
Implementation Method 1
The first ferromagnetic layer and the second ferromagnetic layer are magnetically coupled by exchange coupling via the first interposed layer, the second interposed layer, and the magnetic coupling layer such that magnetization directions of the first ferromagnetic layer and the second ferromagnetic layer are antiparallel to each other
Implementation Method 2
Such diffusion of elements in the interface is caused by, for example, activation of an interface region caused by plasma at the time of forming each layer constituting the SAF structure using sputtering
Implementation Method 3
activation of the interface region caused by an annealing process in a manufacturing step for the SAF structure, the magnetoresistive effect element, or a device including the magnetoresistive effect element
Data Source
AI summary
A ferromagnetic multilayer film includes first and second magnetization fixed layers, first and second interposed layers, and a magnetic coupling layer. The magnetization fixed layers are antiferromagnetically coupled by exchange coupling via the interposed layers and the magnetic coupling layer. A main element of the magnetic coupling layer is Ru, Rh, or Ir. A main element of the first interposed layer is the same as that of the magnetic coupling layer. A main element of the second interposed layer is different from that of the magnetic coupling layer. A thickness of the first interposed layer is greater than or equal to 1.5 times and less than or equal to 3.2 times an atomic radius of the main element of the first interposed layer. A thickness of the second interposed layer is less than or equal to 1.5 times an atomic radius of the main element of the second interposed layer.