Modeling and Analysis of Magnetic Field-Induced Coupling on Hexagonal MTJ Array

Abstract

The hexagonal array geometry offered considerable merit for storage density enhancement and magnetic tunnel junction (MTJ) etch convenience. However, with the increase in storage density, the magnetic coupling will become an important factor affecting the performance of devices. We modeled the magnetic coupling of the MTJ stack with square and hexagonal arrays, and calculated the intra-cell and inter-cell stray fields with different structural parameters such as the electrical Critical Diameter (eCD) of the MTJ stack and the spacing between MTJ stacks (pitch), and further investigated the inter-cell magnetic coupling coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Psi$ </tex-math></inline-formula> ) and critical switching current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{c}$ </tex-math></inline-formula> ) to characterize the performance of the device. Simulation results show that the intra-cell stray field increases with the decrease of eCD, while the inter-cell stray field decreases with the decrease of eCD and increases with the decrease of pitch. In order to reduce the influence of the inter-cell stray field, the pitch needs to be more than twice of eCD. Therefore, building a hexagonal MTJ storage array with a pitch greater than twice the eCD can maximize the storage density.