Magnetic Memory Device Layer Thickness Optimization

The first magnetic layer is segmented into three sub-layers (first, second, and third layers) with different thicknesses and compositions. This segmentation allows each sub-layer to contribute differently to the overall magnetic properties, enabling simultaneous optimization of thermal disturbance resistance and write current characteristics that cannot be achieved with a uniform layer structure.

Different regions of the first magnetic layer have different local properties: the first layer has greater thickness for thermal stability, the second layer has intermediate thickness for magnetization control, and the third layer has minimal thickness for exchange coupling. This local quality variation enables the element to achieve both high thermal disturbance resistance and low write current.

Rather than using a single thick magnetic layer, the structure segments the first magnetic layer into three thinner sub-layers with specific thickness relationships (first > third, second > first). This segmentation achieves the required thermal stability through cumulative thickness and magnetic moment while maintaining manufacturability and avoiding excessive complexity.

The patent uses composite material structures with alternating magnetic and nonmagnetic layers, where each layer has optimized thickness and composition. The stack structure combines CoFeB, MgFeO, and other materials in specific configurations, creating a composite system that achieves high thermal stability without requiring any single layer to be excessively thick or complex.