CoFeBMo Free Layer Magnetic Junction for Low Current STT-MRAM
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Solution Overview
Problem
Conventional spin transfer torque magnetic random access memories (STT-MRAMs) face challenges in reducing switching current while maintaining thermal stability and high magnetic anisotropy, which affects their performance and efficiency.
Innovation Solution
A magnetic junction with a free layer comprising a CoFeBMo alloy, where the free layer has perpendicular magnetic anisotropy energy greater than out-of-plane demagnetization energy, reducing saturation magnetization and switching current, and enhancing switching speed and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional free layer materials are used, then thermal stability is maintained, but switching current remains high
Solution Approach 1:
The patent changes the material composition parameters of the free layer by incorporating Mo into CoFeB, creating a CoFeBMo alloy with optimized atomic percentages (Co: 30-70%, Fe: 5-40%, B: 5-30%, Mo: 1-20%). This compositional parameter change reduces saturation magnetization while maintaining perpendicular magnetic anisotropy, thereby reducing switching current without sacrificing thermal stability
Solution Approach 2:
The patent creates a composite magnetic alloy CoFeBMo by combining multiple elements (Co, Fe, B, Mo) with complementary properties. Mo addition to CoFeB forms a composite material that leverages the high spin polarization of CoFeB while Mo contributes to reduced magnetization and enhanced anisotropy, achieving both low switching current and high thermal stability
2Speed
If conventional free layer materials are used, then magnetic anisotropy is sufficient, but switching speed is limited
Solution Approach 1:
The patent optimizes the thickness parameter of the CoFeBMo free layer to 3-15 nm, which is critical for achieving perpendicular magnetic anisotropy. This thickness parameter, combined with the specific compositional parameters, creates the right balance between magnetic anisotropy energy and demagnetization energy, enabling fast switching while maintaining compositional stability
Solution Approach 2:
The patent introduces local quality variations through the specific atomic distribution and concentration gradients of Mo within the CoFeB matrix. The non-uniform distribution of Mo atoms creates local magnetic moment variations that enhance perpendicular anisotropy at specific regions, improving switching speed while maintaining overall magnetic stability
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 magnetic junction with the CoFeBMo free layer achieves reduced switching current and improved performance by maintaining high perpendicular magnetic anisotropy, leading to enhanced switching speed and thermal stability in STT-MRAMs.
Implementation Method 1
The free layer has a free layer perpendicular magnetic anisotropy energy greater than a free layer out-of-plane demagnetization energy
Implementation Method 2
A spin polarized current driven through the magnetic junction exerts a spin torque on the magnetic moments in the magnetic junction
Implementation Method 3
reduced saturation magnetization while maintaining a high magnetic anisotropy
Data Source
AI summary
A magnetic junction and method for providing the magnetic junction are described. The magnetic junction resides on a substrate and is usable in a magnetic device. The magnetic junction includes free and pinned layers separated by a nonmagnetic spacer layer. The free layer is switchable between stable magnetic states when a write current is passed through the magnetic junction. The free layer has a free layer perpendicular magnetic anisotropy energy greater than a free layer out-of-plane demagnetization energy. The free layer includes a [CoxFeyBz]uMot layer, where u+t=1, x+y+z=1 and u, t, x, y and z are each nonzero. The [CoxFeyBz]uMot layer has a perpendicular magnetic anisotropy energy greater than its out-of-plane demagnetization energy.